Latest News About Materials................

Goinig green on the green

2009-04-18T10:47:00.000-07:00

Arizona golf ball manufacturer, Dixon, has developed a line of environmentally responsible golf balls. Dixon’s Earth golf ball is “green” throughout and does not contain heavy metals like tungsten, cobalt, lead, or non-renewable synthetic materials and compounds, often found in mainstream products. The ball has a graded-density core made from a proprietary polymer combination that preserves the playable properties of the ball. The ball is fabricated from new materials to ensure consistent playing properties but is 100% recyclable. Dixon works with a local company to recycle the balls into playgrounds, football field turf, etc.
The golf balls are no less playable for being environmentally friendly. In testing, the Dixon Earth ball was found to play better than most two-piece golf balls and out-performed several three-piece, urethane cover balls. It plays the distance, spins, sticks on the greens, and has plenty of “feel” when putting. Each box of Dixon Earth golf balls includes a return mail pouch so golfers can mail used golf balls back to Dixon easily. Introduced earlier this year, the Dixon Earth golf ball conforms to USGA certification standards. Website: www.dixongolf.com.

Aeromat2009 (20th anniversary) - conference & exposition

2009-03-24T23:05:00.000-07:00

Celebrating 20 Years! The premier industry event for the global aerospace community.

Novel & Engineered Materials System
& Processes for the Aerospace Industry

Conference: June 7 -11, 2009
Exposition: June 8-10, 2009
Education Short Courses: June 6 and 11-12, 2009

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A $25 value.

Learn more about hot forming, cold pre-forming and hot sizing. Make it better.

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Like what you see? More valuable information like this will be presented at AeroMat. Learn and network with the authors, get all the latest trends in aerospace materials and processes.

AeroMat covers the topics driving materials technology for aerospace applications through technical presentations, education courses and a dynamic exposition.

AeroMat -- Where Aerospace Industry Leaders Learn and Do Business. AeroMat attracts more than 750 delegates and over 70 exhibiting companies who discuss and display the latest advances in materials and processes for aerospace applications.

Hear presentations from aerospace scientists, engineers and technicians from over a dozen countries around the world
Network with the leaders in aerospace technology, materials and processes from both industry and government
Interact with more than 70 exhibiting companies at the largest trade show exclusively for the aerospace community

Drive sales revenue. Make business contacts. Reserve your space and sponsorship today. View 2009 Exhibitor Prospectus (pdf format).

Aluminum propeller alloy

2009-03-23T12:18:00.000-07:00

An aluminum alloy based on a specific market need is Mercalloy 366, developed by Mercury Marine and now marketed commercially by Alcan. The development of Mercalloy grew from the need to find a durable, easy-to-cast alloy for marine propellers. The material had to provide superior ductility and impact resistance over traditional high pressure die casting alloys in case the propeller hit a rock, stump, or other underwater object. The development of Mercalloy, described in a paper presented at the 110th Metalcasting Congress in 2006 (“Innovations in Marine Propeller Technology: High Ductility Mercalloy 366 Alloy”), shows some of the many tradeoffs and considerations that enter into developing a new material. In this case, the metallurgists were trying to balance the ductility of the alloy with the need to prevent die

soldering.

For example, Al-Si-Mg or 300-series alloys offer many processing advantages such as high fluidity, excellent castability, and good machinability. Strength and ductility can be tailored through chemistry. For example, corrosion resistance is excellent when the copper content is

low. Strength is typically increased as magnesium content is increased. Typically, iron has not been adjusted in 300-series aluminum die casting alloys because removal of iron leads to die soldering. A small amount of iron — in the range of 0.7 to 1.3 wt% — can be added to 300-series die casting alloys to help eliminate soldering, but these small additions significantly degrade the mechanical properties of the cast product. Adding manganese to replace the iron can mitigate soldering, while maintaining ductility and strength. However, manganese forms blocky intermetallic compounds that could limit the amount of ductility gained.

The research team at Mercury Marine sought to eliminate the iron and die soldering without introducing new intermetallic phases. To design the most appropriate alloy, the researchers cast propellers of Mercalloy 366, Silafont-36, and AA 514 (See table below). The alloys

had the following properties.

• Energy absorption: Mercalloy 366 propellers showed the best energy absorption as determined by drop impact testing.

• Deflection: Mercalloy 366 and Silafont-36 propellers demonstrated similar peak loads in load vs. deflection testing. Mercalloy 366 propellers displayed consistently higher deflection in load vs. deflection testing.

• Die soldering: Die soldering issues were not observed in this study and have not been seen in the 250,000 propellers that have been cast since the completion of the research.

The researchers believe Mercalloy achieves its solder resistance through strontium content, as opposed to manganese additions. The lack of any blocky intermetallic phases combined with a finely modified eutectic microstructure is the basis of the increased ductility Mercalloy demonstrates. Although Mercalloy was developed to solve a specific product need, Mercury Marine is now using the alloy for engine drive shaft housing and swivel brackets. Other general market opportunities for the alloy include various brackets and squeeze casting applications for parts such as automotive link arms. Alloy chemistry data for propeller study

Alloying Mercalloy 366, Silafont-36, AA514,

element wt.% wt.% wt.%

Silicon 9.50 9.51 0.49

Strontium 0.0682 0.023 —

Magnesium 0.14 0.13 4.12

Iron 0.20 0.12 0.81

Copper 0.12 o.02 0.13

Manganese 0.28 0.65 0.45

Titanium — 0.04 —

Aluminum Balance Balance Balance

Something about Magnesium (Mg)

2009-03-15T07:36:00.000-07:00

Magnesium and its alloys are being considered for structural applications in every type of vehicle because of their favorable combination of tensile strength, elastic modulus, and low density. Magnesium alloys have high strength-to-weight ratios and relatively good electrical and thermal conductivity, as well as high damping capacity. Magnesium is the eighth most abundant element in the Earth’s crust, and the third most plentiful element dissolved in seawater. Because magnesium is found in seawater, it is available in almost limitless quantities: Acubic mile of seawater contains six million tons of magnesium metal.

Magnesium as a structural material has been up and down during the 20th Century. As the world supply increases and a new legion of energized researchers and scientists address the many aspects of the most abundant structural metal, magnesium will again rebound to new heights. The present trend indicates that China will be a major contributor to this development.

Two major magnesium alloy systems are available. The first includes alloys that contain 2 to 10% aluminum, combined with minor additions of zinc and manganese. These alloys are widely available at moderate cost, and their mechanical properties are good at temperatures up to 95 to 120°C (200 to 250°F). However, above these temperatures properties deteriorate rapidly.

The second group consists of magnesium alloyed with elements such as rare earths, zinc, thorium, silver, and silicon (but not aluminum), all containing a small but effective zirconium content that imparts a fine-grain structure (and thus improved mechanical properties). These alloys generally possess better elevated-temperature properties, but they are more expensive because of their more costly elemental additions and specialized manufacturing technology.

Aluminum metal, which is not easy to get from its ores, has become a 30 million ton per year business, while magnesium has struggled to reach about 800,000 tons per year. Realistically, world production must grow to over one million metric tons per year if it is to be seriously considered for widespread applications. This article discusses the magnesium industry today and what may happen in the future.

Armor kit for Stryker vehicle has frame of high-hard steel

2009-03-09T12:02:00.000-07:00

Allegheny Technologies Incorporated’s next-generation ATI 500-MIL armor steel has been selected for an armored situational awareness kit on the U.S. Army’s Stryker Light Armored

Vehicles, marking the first major legacy-vehicle military application for this specialty metal. The add-on kit, known as the StrykShield, is comprised of front and side transparent armor windows that are mounted in a framework built with ATI 500-MIL high-hard armor steel. Produced by Carapace Armor Technology, the StrykShield kit provides increased visibility and situational awareness for Stryker crews, while providing full ballistic and blast protection.

Allegheny Technologies’ ATI 500-MIL steel is the first new, high-hard steel armor developed in America since the Vietnam conflict, and meets new U.S. MILDTL- 46100E high-hard specifications for ballistic performance. It protects against such threats as armor-piercing rounds while also offering good blast-resistance properties.

ATI 500-MIL armor steel is available in plate form, with sheet product currently in development by ATI. The specialty armor plate is offered in thickness gauges from 3/16 inch to one inch (0.5 to 2.5 cm), and in sizes as large as 96 X 300 inches (243 X 763 cm), with customized manufacturing solutions available to meet customers’ specific needs. www.alleghenytechnologies.com

Accessory helps vehicles get a grip

2009-03-08T08:27:00.000-07:00

Snobootz, a lightweight, patent-pending, winter traction device for passenger cars and light trucks consists of a durable fabric boot that wraps around the tire. The product features rubber traction pads embedded with steel cleats bonded to the fabric boot for aggressive ice traction. Snobootz fits most popular size tires on cars and light trucks, even vehicles with tight clearances that cannot use chains.

To install Snobootz, the driver drapes the boot over the tire, drives forward a few feet, and latches the hook-and-loop fastener which holds the boot on the tire.

In independent tests at Michigan Tech University’s Keweenaw Research Center (KRC), a full-size SUV equipped with Snobootz was about 20 percent faster than a chain-equipped vehicle on ice from zero to 20 mph. On a 10 percent ice-covered grade, the vehicle equipped with Snobootz was able to climb, come to a complete stop on the slope, and continue the climb without sliding backwards.

Snobootz can be installed 66 percent faster than tire chains, meaning less exposure of the driver to roadside hazards. Also, at one-third the weight of chains, Snobootz are easier to handle and store. Although not designed for extended use on dry pavement, the tough rubber traction pads have been proven to last more than 200 miles, exceeding the life expectancy of tire chains on dry pavement.

Snobootz come as a set of two to cover both tires on the drive axle.

For further information visit http://www.snobootz.com

Fluorescent fish

2009-03-07T09:03:00.000-08:00

Scientists have discovered that certain fish are capable of glowing red. Nico Michiels, from the University of Tübingen, Germany, led a team who captured the striking images of red fluorescence among marine fish. They speculate that it may function as a communication or attraction signal.

For more informations: www.alphagalileo.org/ index.cfmfuseaction= readrelease&releaseid= 532150

Carbon fiber composite body over a chrome-moly chassis

2009-03-07T01:00:00.000-08:00

This Ronn Motor Co. Black Scorpion hybrid has a carbon fiber composite body over a chrome-moly chassis. It is powered by the company’s hydrogen-on-demand system, which provides 130-octane hydrogen in real time, blended with gasoline in ratios of 30 to 50%. For more details about how this works and information about how to buy your very own Scorpion,

For more information visit http://ronnmotors.com.

Mars Lander finds water

2009-03-06T10:36:00.000-08:00

Laboratory tests aboard NASA’s Phoenix Mars Lander have identified water in a soil sample. The lander’s robotic arm delivered the sample to an instrument that identifies vapors produced by the heating of samples.

“This is the first time Martian water has been touched and tasted,” says William Boynton of the University of Arizona, lead scientist for the Thermal and Evolved-Gas Analyzer.

For lots more about the Phoenix, visit

www.nasa.gov/mission_pages/phoenix/news/phoenix-20080731.html.

Tailored surface coatings enhance interconnect materials

2009-03-04T10:37:00.000-08:00

Tailor-made stainless steels pre-coated with cobalt combine excellent high-temperatur corrosion resistance with good surface conductivity for fuel-cell interconnects, according to Sandvik Surface Technology, Sweden. Sandvik Sanergy HT is made via normal industrial strip production routes, and the coating is applied in a continuous process.

The pre-coated strip can reduce the solid-oxide fuel cell (SOFC) production process by enabling fewer process steps and ease of handling. Because the material is gas tight, it allows thin plates within the fuel cell, and is designed to closely mimic the expansion of ceramic materials in SOFCs.

It has low a degradation rate in fuel cell applications as a result of the cobalt coating, which reduces the electrical resistance of the surface as well as minimizing chromium evaporation. Carefully controlled chemical composition of the steel, with the addition of molybdenum and niobium, improves its high temperature strength and oxidation resistance.

For more information: Sandvik Materials Technology, Sandviken, Sweden; tel: 46 26 26 30 00;

fax: 46 26 25 17 10; www.smt.sandvik.com/surftech.

MICROSTRUCTURAL REFINEMENT OF A EUTECTOID FE-NI-MN-AL ALLOY

2009-03-02T03:54:00.000-08:00

Anovel two-phase alloy of composition Fe- 20Ni-35Mn-15Al (all compositions in atomic percent) was produced by arc melting. Disk samples of 3 mm diameter were electro-polished in a mixture of 20% nitric acid, 10% butoxyethanol, and 70% methanol by volume at 253K (–20°C, –4°F).

The resulting thin foils were examined in a Technai F20 field emission gun TEM operated at 200 kV. Selected area diffraction showed that the phases present were B2 (ordered body centered cubic) and face-centered cubic. The alloy consisted of alternating ~200 nm wide B2 and ~500 nm wide FCC lamellae, as shown in Fig. 1. The compositions of the B2 and FCC phases were determined by EDS to be Ni-28Al-18Mn-7Fe and Fe-37Mn-7Ni-6Al, respectively.

Fig. 1 — Brightfield TEM image showing the as-cast

microstructure of Fe-20Ni-35Mn-15Al, which consists of

alternating lamellae of B2 (dark) and FCC (light) phases.

The as-cast alloy was subsequently heated in argon to 1573K (1300°C, 2370°F), which is above the eutectoid transformation temperature, and quenched into water. Very fine features were formed in the quenched specimen. These features consisted of 50 to 70 nm wide B2, and 80 to 150 nm wide FCC lamellae, as shown in Fig. 2. Asubstantial Vickers hardness increase from the as-cast hardness of HV310 to HV380 occurred due to this microstructural refinement.

Fig. 2 — Brightfield TEM image showing the refinement in

microstructure of Fe-20Ni-35Mn-15Al after quenching,

which consists of alternating finely-spaced B2 (dark) and

FCC (light) phases.

For more information: Prof. Ian Baker, Thayer School of Engineering, Dartmouth College, Hanover, NH 03755; tel: 603/646-2184; ian.baker@dartmouth.edu;

www.dartmouth.edu.

Surface of gold nanorods designed to deliver drugs

2009-02-28T22:23:00.000-08:00

Ways to change the surface of gold nanorods to enable drug delivery and other functions are being studied by scientists at the Massachusetts Institute of Technology, Cambridge. Gold nanorods are tiny cylinders of gold, about 10 nm wide and 40 nm long. They differ from spherical gold nanoparticles in that they can absorb infrared light. That means they can theoretically be activated to deliver drugs or other materials by infrared lasers without damaging surrounding cells, which do not absorb infrared light.

However, scientists must first figure out how to deal with an organic molecule known as CTAB that coats the outer surface of gold nanorods and tends to detach from and reattach itself to the surface. The molecule, a byproduct of the synthesis reaction that produces the nanorods, makes it difficult to attach other molecules such as drugs or DNA.

Researchers found that a low concentration of the CTAB in the surrounding surface accelerates heat dissipation after the nanorod is hit with infrared light. When the concentration of CTAB is high, heat is dissipated more slowly. That information could help scientists design

nanorods that fight cancer agents by burning away tumor cells when activated with infrared light. “The surface chemistry is really key to everything,” says Prof. Kimberly Hamad-Schifferli.

For more information: Kimberly Hamad-Schifferli, Massachusetts Institute of Technology,

Cambridge, MA 02139; tel: 617/452-2385; schiffer@mit.edu; www.mit.edu.

Superplastic Forming

2009-02-27T03:55:00.000-08:00

Vacuum Forming

Vacuum forming is a superplastic forming process in which a gas pressure differential is imposed on the superplastic diaphragm, causing the material to form into the die configuration. Sometimes called stretch forming, the applied pressure is limited to atmospheric pressure (that is, 100 kPa, or 15 psi), and the forming rate and capability are therefore limited.

The rate of pressurization in blow forming is normally established such that the induced strain rates in the forming sheet are maintained in the superplastic range. The rate of pressurization is determined by trial and error, or by the application of analytical modeling methods. This pressure is generally applied slowly rather than abruptly to prevent too rapid a strain rate and consequent rupturing of the material. This information

With blow forming, additional pressure is applied from a gas pressure reservoir, and the only limitations are related to the pressure rating of the system and the pressure of the gas source. A maximum pressure of 690 to 3400 kPa (100 to 500 psi) is typically used in this process. The blow forming method is illustrated in the diagram, which shows a cross section of the dies and forming diaphragm. In this process, the dies and sheet

material are normally maintained at the forming temperature, and the gas pressure is imposed over the sheet, causing the sheet to form into the lower die; the gas within the lower die chamber is simply vented to the atmosphere. The lower die chamber can also be held under vacuum, or a

back pressure can be imposed to suppress cavitation if necessary.

materials community ( http://materialsengineers.co.cc )

Antimicrobial Properties Of Copper Alloy Surface

2009-02-24T05:16:00.000-08:00

Recent laboratory studies show that several different types of bacteria die when they come in contact with dry copper and copper alloy surfaces at room temperature. In fact, the numbers drop to zero on copper alloys in one to two hours. These results suggest that the selection of copper alloys for surfaces exposed to human touch can materially assist in reducing bacterial contamination.

To make antimicrobial claims in the United States, the approval of the U.S. Environmental Protection Agency (EPA) is required. It is anticipated that regulatory approval will facilitate the introduction of antimicrobial copper alloys in hospitals, nursing homes, and other healthcare facilities, as well as schools, and public buildings.

Antimicrobial properties

Man exploited the antimicrobial attributes of copper long before the nineteenth century, when Louis Pasteur developed his germ theory of disease. The Hippocrates Collection, 460 to 380 B.C., to which the father of medicine contributed, recommends the use of copper for leg ulcers related to varicose veins. Pliny, 23 to 79 A.D., used copper oxide with honey to treat intestinal worms. The Aztecs gargled with a mixture containing copper to treat sore throats.

In a recent laboratory study, water inoculated with a fecal indicator bacterium, Escherichia coli, was stored in water vessels made of brass, a copper alloy, as well as in earthenware vessels. The vessels contained either distilled water or natural water from the Punjab region in rural India. No live bacteria were found in the brass vessels after 48 hours,

while the water in the earthenware vessel remained contaminated.

formation, in pursuit of FIFRA registration. When registration is granted, antimicrobial copper alloys will be the first solid materials legally permitted to make public health claims.

MRSAstudies

The viability of Methicillin-Resistant Staphylococcus aureus (MRSA) was measured on the surfaces of four alloys. The bacterial counts were taken on C197, an alloy containing 99% copper; C240, a brass; C770, a copper nickel zinc alloy; and S304, the experimental control. On C197, a rapid seven-log falloff to zero is seen within 75 minutes, while on C220 a uniform seven-log drop to zero occurs in 270 minutes. In C770, a three-log drop is observed after 270 minutes. However, the three-log drop indicates only ten thousand out of ten million bacteria survived, which corresponds to a 99.9% reduction in live bacteria.

Copper in hospitals

Initially, copper alloys will be introduced into hospitals as surfaces and objects that humans frequently touch. Specific applications within hospitals include door hardware, sink faucet handles, IV drip stands, bed rails and footboards, over-thepatient tables, nurse’s call buttons and work stations, furniture pulls, instrument knobs, arms of chairs and other routinely touched surfaces within the healthcare setting. Copper alloys should also be used in nursing homes, assisted living facilifacilities, schools, public buildings, exercise facilities, shopping malls, mass transit systems, airports, the interiors of passenger aircraft and cruise ships, and even in the home.

The attainment of EPAapproval is the first of several barriers to introducing copper alloys into hospitals. The applications with the highest likelihood of success are being identified, and the entire supply chain is being engaged. Clinical trials are underway. Copper alloy components are being fabricated and made readily available. Insight into the decision-making process in hospitals is gained and better understood. It is necessary to gain acceptance among hospital administrators, infection control practitioners, government healthcare officials and the general public, as well as architectural firms engaged in hospital construction. Widespread application of copper alloys should significantly decrease the number of viable bacteria found on human touch surfaces. The net result should be an increase in copper alloy utilization, a reduction in nosocomial infections and ultimately, the saving of lives. Success will be attained when it is generally understood and appreciated that copper alloys should be utilized in those applications where their unique and intrinsic antimicrobial properties will benefit human health.

For more information: Harold T. Michels, Copper Development

Association Inc., New York, NY 10016; tel:

212/251-7224; www.copper.org.

Materials in the "BMW SAUBER FORMULA ONE RACE CAR"

2009-02-21T00:07:00.000-08:00

With the exception of the engine, gearbox, and wheel carriers, a Formula One car is made almost exclusively of carbon fiber composites. High rigidity and strength, coupled with very low weight, are the stand-out attributes of carbon fibers. It has rigidity similar to that of steel, but is around five times lighter. On the downside, the manufacturing processes involved in making it are highlycomplex and its material price is considerable.
One square meter of pre-impregnated carbonfiber sheeting costs between $69 and $276. Carbon fibers have a diameter of five to eight micrometers. Typically, between 1,000 and some 20,000 fibers are brought together into bundles, and these are woven into textile-like structures.

Around 20 different types of carbon-fiber material are used in Formula One. These differ most
prominently from one another in their structure and the type of resin with which they are impregnated. Should the forces only be coming in from one direction, unidirectional weave is used. If they are being exerted from various different directions, on the other hand, bidirectional weave is preferred.
In order to provide the properties desired, specialist composite engineers establish which weave is required, in which resin and in how many layers.
The manufacturing process involved in making a carbon-fiber part incorporates several stages. First the part is designed using computer-based CAD (Computer Aided Design) techniques. This data is then refined and provides the basis for CAM (Computer Aided Manufacturing). The mold is cut into a tooling block on a five-axis milling machine; this block serves as the positive mold. The laminators place the precisely pre-cut carbon-fiber pieces one after the other onto the tooling block following plans drawn up by the composite engineers. When this stage has been completed, the whole item is packed into a polythene bag, vacuumized and cured for between ten and 20 hours in the autoclave at a temperature of around 50°C (120°F). After some final touches, the negative mold is then ready to be manufactured into the carbon-fibre part itself.

The laminators lay the pre-molded carbon-fiber pieces on top of and along-side each other in the
negative mold. Depending on the part in question, this can involve as many as several hundred pieces. When everything is ready, the mold – plus carbonfiber inlay – is also packed into a polythene bag, vacuumized and cured for five to six hours at a temperature of about 150°C. When the curing process is over, the individual parts are further refined and brought together into finished components. Afront wing, for example, consists of around 20 separate carbon-fiber parts.
Components that need to demonstrate particular toughness are made with Kevlar as well as carbon fiber. The Kevlar used by the BMW Sauber F1 Team is produced and supplied by its partner DuPont.

UAV fuselage to be made of carbon fiber composites

2009-02-19T06:18:00.000-08:00

Advanced Composites Group Ltd., U.K., has been selected by Schiebel Corp., Vienna, Austria, as one of its preferred suppliers of material for its Camcopter S-100 Unmanned Air Vehicle (UAV). It measures about ten feet long by 3.5 feet high by four feet wide, with a rotor diameter of about 11 feet. It is capable of carrying a 55-pound payload for up to six hours. MTM 49 and prepregs were selected for the manufacture of the carbon-fiber monocoque fuselage, and LTM 212 prepregs were selected for tooling.

The MTM49 component prepreg cures at 80 to 160°C (176 to 320°F). It is a toughened epoxy matrix resin specifically formulated for the manufacture of components requiring excellent ambient and hot mechanical performance combined with good impact resistance. It exhibits a good balance of temperature resistance and toughness properties.

The LTM212 tooling prepreg system is based on proprietary low-temperature cure epoxybased
formulations that may be post-cured to produce high service-temperature tooling capable of withstanding 210°C (410°F). At ambient temperature, LTM212 offers a maximum drape life of two and a half days, and is autoclave-workable for four days.

Can you identify this corrosion type?

2009-02-17T08:23:00.000-08:00

I have an image of corroded steel plate.I found this one from a ship.This is a cargo vessel.So i want to fin out the corrosion type of this plate.Not only blisters appear on the surface, there some areas having pits.Normally we can think it as a hydrogen blistering.But this plate is not placed in a acidic medium.Is there any possibility for hydrogen blistering without any acidic medium or is this another type of corrosion? can you explain this one.

At the same time i was able to see a ultra sonic testing.Below video present how it was done.Actually we tested same plate as seen in above image.Because of this corrosion plate thickness of the steel plate reduce 11mm to around 9mm,with in 2 years.

Polyimide nanocomposite protects space vehicles

2009-02-17T07:07:00.000-08:00

A colorless, sprayable polyimide nanocomposite coating that protects spacecraft from radiation and atomic oxygen erosion has reportedly been developed by ManTech International
Corp., Huntsville, Ala. Called Corin XLS, the polyimide nanocomposite was developed with funding from the Air Force Research Laboratory as a coating for high-strength fibers exposed to atomic oxygen and UV degradation in low-earth orbit.
The material offers temperature stability common to most polyimides, but adds high optical clarity, room-temperature cure, and unmatched resistance to degradation from atomic oxygen and anisotropic plasma etching. It has been recognized by R&D Magazine as one of the top 100 most innovative and technologically significant new products of the year.

Ultrasonic Image Analysis Of Steel Slabs

2009-02-17T06:13:00.000-08:00

The soundness of continuously cast slabs that were accelerated-cooled prior to completion of the gamma to alpha transformation has been evaluated in a project at the University of Pittsburgh. To achieve this objective, an ultrasonic NDT technique was selected to assess the level of anomalies or defects in the slabs. The results from the analysis were evaluated with the aid of software developed to identify the type of defects and their location in the slabs. These results were complemented with a systematic microstructural analysis.

Ultrasonic testing:
The ultrasonic NDT image can be processed and analyzed to give qualitative characterization of the defects in a continuously cast steel slab. The ultrasonic sensor and its compatible software can provide information regarding the distribution, location, and density of the defects. The specific objectives of this work were to:
• Assess the level of anomalies or defects in the
steel slabs via ultrasonic testing.
• Identify the types of defects and locations in the slabs by ultrasonic testing and specially developed software.
• Verify the result via direct microstructural analysis.
In this project, ultrasonic NDT and direct microstructural analysis were conducted on 24 samples of the three grades of steel 1010, 1091, and 1319. The samples were cut from four different locations from the as-received steel slabs. The slabs having thicknesses of 175 to 230 mm were grouped in two sets based on the cooling conditions provided by the steel company supporting this work. The slab samples were either air cooled or cooled in a cooling chamber to room temperature. The temperature at which the slabs were introduced into the chamber
was between 550 and 570°C (1020 and 1060°F). Based on this information, it appears that the slabs enter the cooling chamber after austenite has largely decomposed to either high- or low-temperature products. That is, the slabs enter the cooling chamber at subcritical temperatures.
In ultrasonic NDT testing, ultrasonic signal waves are emitted from a sensor made up of a piezoelectric transducer and a receiver. Aschematic view of the ultrasonic mechanism can be seen in Fig 1(a). Parts of the emitted waves are reflected by anomalies to the transducer or other electronic receivers, and other portions of waves are scattered and damped into the texture. The magnitude of initial input pulls and captured reflected signals can be compared by an oscilloscope, or by a collecting and compiling signal software. Sonics is a DOS software package used for this purpose in these tests. The ultrasonic tests were carried out in a bath filled with 160 liters of water, to minimize the undesirable sound waves from environments and equipment that may have changed the image of the results. An image of the ultrasonic machine is shown in
Figure 1 (b). Scatter in the energy of the waves traveling through the sample because of obstacles, gives information about the anomalies. The sensor moves with a constant speed and scans the surface of the sample. An overlapping of scanning is considered to remove the uncertainty of the signals received from the edges of the scanning beam band. Accuracy of the images and speed of scanning depend on the sensitivity of the sensor.
The economical advantage of NDT tests over destructive testing is obvious, but the disadvantages are the level of accuracy and the strength or detail of the information. This work used NDT analysis to locate the presence of a defect and micro structural analysis to assess the type and size of the defect. The method of image processing of ultrasonic time-of-flight maps introduced in this work using the Microsoft Excel macro offers a promising processing and analysis tool to specify the type and location of anomalies observed in the continuously
cast slabs cooled from different thermal path conditions. This method can be used to test the internal soundness of slabs that have been accelerated cooled to room temperature. This summary has outlined the procedures detailed in Using NDT Image Processing Analysis to Study the Soundness and Cleanliness of Accelerated Cooled Continuously Cast Steel Slabs.

Development of Advanced Titanium Welding Processes for Improved Material Utilization in Aerospace Manufacturing

2009-02-16T06:39:00.000-08:00

Laser welding of titanium 6Al-4V has been developed for producing near net shape structural components. Process parameters have been identified for producing very repeatable, high-quality welds on a variety of material thicknesses and joint configurations.

Extensive metallurgical examinations and preliminary mechanical property evaluations have been done to qualify this process for fabricating structural parts. It has been found that the mechanical properties of automated laser welded titanium joints are very close to the same as the parent metal, and that equivalent performance can be achieved with a minimal weight increase. Furthermore, the statistical variance in the mechanical test data is very low, which is extremely important for efficient design of any performance-critical part as a welded structure.

In addition to laser welding, friction stir welding of titanium 6Al-4V is being developed for a variety of thicknesses and joint configurations. Friction stir welding is a solid-state process capable of retaining the microstructural integrity of the parent material. This makes it very attractive for fatigue-critical and damage-tolerant primary air frame structures. Preliminary
mechanical test data has shown that the fatigue properties of FSW titanium butt joints are
comparable to those of the parent material.

The primary difficulty in the development of heavy gage titanium FSW was to identify the tooling designs and process parameters for producing defect free joints. Finally, by combining one of these advanced welding techniques with hot forming, near net shape parts can be produced with aerospace quality dimensional tolerances at a dramatically improved
material utilization level

Aero industries need more advanced materials

2009-02-15T06:42:00.001-08:00

The aerospace industry, which is largely responsible for development of advanced alloys that benefit a range of other industries. More than any other group, aircraft manufacturers rely on the steady improvement of materials and fabrication methods for increased efficiency, higher speeds, and greater reliability and durability. Because of the efforts put forth by a multitude of engineers and scientists, aerospace has become one of the few success stories in American manufacturing. It is a growing industry, with exports of both airplanes and their materials of construction. In particular, titanium alloy developments enable smaller, more powerful engines and lighter-weight structures. Composites, which were formerly considered to expensive for commercial aircraft, are increasingly the material of choice for many aircraft structures. Titanium’s compatibility with composites has increased its use on advanced aircraft, but has also raised concerns about reliable supply.
Once considered a major drawback, the supply is about to grow as Allegheny Technologies Inc. builds new titanium-sponge plants in Oregon and Utah. The first new titanium sponge plants in the United States in 60 years, they represent an assured reliable source for both the U.S. and foreign aircraft industries. However, titanium remains an expensive material, and ways to reduce component cost are underway across the industry. For example, NASA is developing Electron Beam Freeform Fabrication (EBF3), an additive metal process in which an electron beam, wire feed, and computer control build near-net-shape components, either by addition of details onto a simplified preform, or by fabricating the entire component. The EBF3 process can reduce high buy-to-fly ratios (12:1 to 20:1 are not uncommon for some components) down to less than 5:1. Laser welding of Ti-6Al-4V has been developed at Boeing and the Edison Welding Institute for producing near-net-shape structural components. In addition to laser welding, friction stir welding of Ti-6Al-4V is being modified for a variety of thicknesses and joint configurations.

Hot Stretch Forming (HSF), developed by the Cyril Bath Co., combines traditional stretch forming technology with hot metal forming techniques. HSF allows engineers to design a variety of titanium structure profiles that are curved to a specific, precise radius prior to final machining. Plasma transferred arc welding torches that serve as the high-energy source for additive manufacturing have been designed by MER Corp. In addition to the low cost fabrication of metallic structures, this technology has also been used to form very hard surface layers that are functionally graded to the substrate of a cermet composition.

Not a scary skeleton

2009-02-13T23:55:00.000-08:00

This not-very-scary aluminum skeleton was machined from a chunk of aluminum only 6 by 12 inches in size. It’s one of many machined at the IMTS show on an AgieCharmilles Mikron UCP 600 Vario machining center. A life-size skeleton was scanned by Capture 3D, which turned it into toolpaths. Seco Tools did the machining to show that it can produce orthopedic parts to tolerances of 0.01 inches.
www.secotools.com

Liquid mirror for the moon

2009-02-13T23:28:00.001-08:00

Liquid mirror for the moon Ionic liquids that remain molten even at liquid-nitrogen temperatures are under development at NASA Ames Research Center as mirrors for telescopes on the moon. A spinning mirror of an ionic liquid can be coated with an ultrathin layer of silver just as if it were a solid mirror. Weirdest of all, the silver layer is so thin — only 50 to 100 nanometers — that it actually solidifies. In the vacuum of space, a liquid mirror coated with a thin solid layer of silver would neither evaporate nor tarnish.

For more information, visit
http:// science.nasa.gov/ headlines/y2008/09oct_ liquidmirror.htm

Alcoa supplies aluminum spaceframe for new Ferrari

2009-02-12T08:40:00.000-08:00

The all-aluminum spaceframe for the upcoming Ferrari California sports car is being supplied by Alcoa Wheel and Transportation Products,Cleveland, Ohio। The aluminum spaceframe helps increase performance while lowering vehicleweight to deliver increased fuel economy and lower CO2 emissions. The California, recently unveiled at the Paris International Motor Show, is the latest performance vehicle from Ferrari. The strength and lightweight advantages of aluminum allow Ferrari to maximize performance, strength, and structural rigidity of the California. Alcoa’s spaceframe manufacturing facility is located in Modena, Italy, very close to the Ferrari plant. www.alcoa.com

Friction stir welding joins titanium, steel, and nickel

2009-02-11T09:15:00.000-08:00

Friction stir welding techniques for joining titanium, steel, and nickel-base alloys in thickness ranging up to one inch in a single pass have reportedly been developed at the Edison Welding Institute, Columbus, Ohio. Once a technology only applicable for joining aluminum, FSW has advanced rapidly since its inception in the early 1990s. EWI has applied the technology to tita-nium structures, and has demonstrated the capability to produce full-penetration joints in both corner and T-joint geometries. FSW can be applied to reduce the fabrication cost of structures by producing thick-section, solid-state joints in a single pass without the need for welding consum-ables. Because it is a solid-state process, the base material is never melted. As a result, the process is suitable for joining “non-weldable” materials, often resulting in base metal properties and ex-tremely low distortion.

For more information: Jeff Bernath, Edison Welding Institute, 1250 Arthur E. Adams Drive,

Columbus, OH 43221-3585; tel: 614/688-5085; jeff_bernath@ewi.org; www.ewi.org.

Five-layer aluminum brazing sheet builds heat exchangers

2009-02-09T10:33:00.000-08:00

Five-layer composite aluminum brazing sheet material has been designed for the automotive heat exchanger market at Alcoa’s Heat Exchanger Technical Center in Lancaster, Pa. Alcoa collaborated with Delphi Thermal Systems to design the brazing sheet material that is ultra corrosion resistant and eliminates the need for a chromate conversion coating. Delphi’s switch to the new product reduces fabricating costs for air-conditioning evaporators, improves workflow processes, and makes the evaporator easily recyclable after its service life.

Material choices determine the characteristics of the composite. For example, the intermediate cladding layers may contain zinc to sacrificially protect the core in a corrosive environment, or

the intermediate cladding layers may exhibit excellent inherent resistance to corrosion.

Alcoa’s multiple-layer composites use three corrosion-resistance-enhancing mechanisms to achieve exceptional resistance to perforation by corrosion. Different compositions for the intermediate claddings and the core establish a galvanic potential between the components such that the intermediate cladding layer is anodic to the core. Diffusion of silicon into the core during brazing creates a manganese-depleted zone at the interface between the core and intermediate cladding; this zone is anodic to the remainder of the core. Elevated titanium concentration in the core alloy reduces intergranular corrosion and promotes lateral corrosion in the core.

Fatigue Crack Propagation

2009-02-08T00:26:00.000-08:00

Basically, fatigue crack propagation can be divided into three stages: stage I (short cracks), stage II (long cracks) and stage III (final fracture).

• Stage I: Once initiated, a fatigue crack propagates along high shear stress planes (45 degrees), as schematically represented in Fig. 1. This is known as stage I or the short crack growth propagation stage. The crack propagates until it is decelerated by a microstructural barrier such as a grain boundary, inclusions, or pearlitic zones, which cannot accommodate the initial crack growth direction. Therefore, grain refinement is capable of increasing fatigue strength of the material by the insertion of a large quantity of microstructural barriers, i.e. grain boundaries, which have to be overcome in the stage I of propagation. Surface mechanical treatments such as shot peening and surface rolling, contribute to the increase in the number of microstructural barriers per unit of length due to the flattening of the grains.

• Stage II: When the stress intensity factor K increases as a consequence of crack growth or higher applied loads, slips start to develop in different planes close to the crack tip, initiating stage II. While stage I is orientated 45 degrees in relation to the applied load, propagation in stage II is perpendicular to the load direction, as depicted in Fig. 1. An important characteristic of stage II is the presence of surface ripples known as “striations,” which are visible with the aid of a scanning electron microscope. Not all engineering materials exhibit striations. They are clearly seen in pure metals and many ductile alloys such as aluminum. In steels, they are frequently observed in cold-worked alloys. Figure 2 shows examples of fatigue striations in an interstitial-free steel and in aluminum alloys. The most accepted mechanism for the formation of striations on the fatigue fracture surface of ductile metals, is the successive blunting and re-sharpening of the crack tip.

• Stage III: Finally, stage III is related to unstable crack growth as Kmax approaches KIC. At this stage, crack growth is controlled by static modes of failure and is very sensitive to the microstructure, load ratio, and stress state (plane stress or plane strain loading). Macroscopically, the fatigue fracture surface can be divided into two distinct regions, as shown by Fig. 4.The first region corresponds to the stable fatigue crack growth and presents a smooth aspect due to the friction between the crack wake faces. Sometimes, concentric marks known as “beach marks” can be seen on the fatigue fracture surface, as a result of successive arrests or decrease in the rate of fatigue crack growth due to a temporary load drop, or due to an overload that introduces a compressive residual stress field ahead of the crack tip.

• Final fracture: The other region corresponds to the final fracture and presents a fibrous and irregular aspect. In this region, the fracture can be either brittle or ductile, depending on the mechanical properties of the material, dimensions of the part, and loading conditions. The exact fraction of area of each region depends on the applied load level. High applied loads result in a small stable crack propagation area, as depicted in Fig. 4. On the other hand, if lower loads are applied, the crack will have to grow longer before the applied stress intensity factor K, reaches the fracture toughness value of the material, resulting in a smaller area of fast fracture, Fig. 4b.

• Ratcheting marks: Ratcheting

marks are another macroscopic feature that can be observed in fatigue fracture surfaces. These marks originate when multiple cracks, nucleated at different points, join together, creating steps on the fracture surface. Therefore, counting the number of ratchet marks is a good indication of the number of nucleation sites. Figure 5 presents in

detail some ratchet marks found on the fracture surface of a large SAE 1045 rotating shaft fractured by fatigue.

Overview of None Destructive Testing

2009-02-04T22:41:00.000-08:00

Nondestructive Testing (NDT) and inspection techniques for detecting and evaluating flaws (irregularities or discontinuities) or leaks in engineering systems are reviewed in this article. Of the many different NDT techniques, liquid penetrant and magnetic particle testing account for about half of all nondestructive tests. Ultrasonic and X-ray methods account for about another third, eddy current testing about 10%, and all other methods for only about 2%. Table 1 is a simplified breakdown of the complexity and relative requirements of the five most frequently used NDT techniques. Table 2 compares common NDT methods.

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FLOWFORMING MORTAR

2009-02-04T09:04:00.001-08:00

Flowformed nickel-base alloy mortar barrels have been fabricated in a program jointly funded by the U.S. Army’s Armament Research Development and Engineering Center (ARDEC) headquartered at Picatinny Arsenal, N.J., and the U.S. Marine Corps, Office of Naval Research, Arlington, Va. The goal of the joint program was to demonstrate that lightweight flowformed mortar barrel tubes could be quickly produced, at a cost 50% to 75% less than existing steel barrels, and with lower weight. Two years after the project was approved, prototype flowformed cannon barrels were successfully fatigue-tested and live-fire tested (Fig. 1) at the Yuma Proving Grounds in Arizona, and more Army personnel were added to the development program. Steel mortar systems Today, the United States Armed Forces operate

three different types of mortar systems.

• The 60 mm M224 has a range of up to 3490 meters

(about two miles).

• The 81 mm M252 is the preferred system for

long-range, indirect fire.

• The 120 mm M120/M121 is used for close and

continuous fire.

Each of these mortar systems is comprised of four sections: the cannon or gun tube, bipod, baseplate, and sight unit. The 60 mm and 81 mm mortar cannon barrels are carried, but the 120-mm barrels are vehicle transported. For this reason, it was decided to first focus re-engineering efforts on reducing the weight of the 60 mm and 81 mm barrels. Today, these two mortar barrels are made via conventional manufacturing processes that include machining solid steel forgings into a thick-wall cannon tube. After that, many hours of machining are required to remove steel on both the inner and outer diameters before the mortar tubes are machined to net shape. The incumbent steel has been used for mortar tubes for decades. This steel has excellent fatigue characteristics, but its strength wanes at elevated temperatures. Consequently, thick walls have always been required on steel mortar cannon tubes because, under heavy fire, the mortar tube can reach maximum temperatures of 1100°F, and the

steel’s strength is significantly reduced. Erosion of the steel tubes has also been a problem. Each time a round is fired, the wall thickness is scrubbed off on a micro-level. Eventually, the wall thickness is worn so thin that the cannon tube is condemned and pulled from the battlefield. In spite of great progress in both manufacturing technologies and advanced materials over the past century, these steel cannon tubes had not changed much.

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Theoretical model predicts strength of metals at nanoscale

2009-02-03T04:56:00.000-08:00

A theoretical model designed to predict the strength of metals at the nanoscale has reportedly bee constructed by materials scientists at the University of Pennsylvania, Philadelphia. With this model, they have found that, while metals tend to be stronger at nanoscale volumes, their strengths saturate at around 10 to 50 nm diameter, at which point they also become more sensitive to temperature and strain rate. For example, a gold wire 200 nm in diameter can be 50 times stronger per area than centimeter-size single crystal gold. Penn Prof. Ju Li and his collaborators at the Georgia Institute of Technology combined transition state theory, atomistic energy landscape calculations, and computer simulation to establish a

theoretical framework that predicts the strength of small-volume materials. Unlike previous

models, their predictions can be directly compared with experiments at realistic temperatures

and loading rates. Results show that in large volumes, it is easy for dislocations to multiply and entangle and thus maintain a large population inside the sample; however, in small-volumes, dislocations could show up and then exit the sample, one at a time. To initiate and sustain plastic flow in this case, dislocations need to be frequently nucleated fresh from the surface.

For more information: Ju Li, University of Pennsylvania, Philadelphia, PA19104; tel: 215/898-

1558; liju@seas.upenn.edu; www.upenn.edu.

Superplasticity

2009-02-03T00:43:00.000-08:00

Superplasticity has several different variations in terms of microstructural mechanisms and deformation conditions,. These include

• Micrograin superplasticity

• Transformation superplasticity

• Internal stress superplasticity At this time, only micrograin superplasticity is of importance in the fabrication of parts. For micrograin superplasticity, high ductilities are observed only under certain conditions, and the basic requirements are:

• Very fine grain size material (on the order of 10

m, or 400 in., or finer).

• A controlled strain rate, usually 0.0001 to 0.1/sec.

• Relatively high temperature, greater than approximately one-half the absolute melting point.

A current research goal is development of finer-grain materials that exhibit superplasticity at

lower forming temperatures. Characteristics of superplastic metals Only a limited number of

commercial alloys are superplastic, and these are formed via methods and conditions that are different from those for conventional metals. However, more and more alloys have been grain-refined to induce superplasticity. For a superplastic metal that is tensile tested under proper conditions of temperature, the observed ductility is seen to vary substantially with strain

rate, as shown in the graph for a zinc-aluminum eutectoid alloy. As shown, ductility reaches a

maximum at a specific strain rate, with significant losses in ductility as the strain rate is increased or decreased relative to this maximum. It is well known that the primary factor related to this behavior is the rate of change of flow stress with strain rate, usually measured and reported as m, the strain-rate sensitivity exponent:

where (delta) is the flow stress, and (fsilon’) is the strain rate.

The characteristics of superplastic alloys indicate that unusual forming capability should be possible, but control of forming process parameters is important to reach the full potential of this class of material. Such process controls are more demanding than corresponding requirements for conventional forming processes, and the superplastic forming of sheet metals is a technology that is different from the conventional processes. However, superplastic forming offers advantages over other fabrication methods in that complex components can be fabricated in a single step.

TITANIUM INVESTMENT CASTINGS

2009-02-01T22:44:00.000-08:00

Large, complex titanium shapes for a variety of aero-engine and structural components are increasingly being investment cast. For example, Fig. 1 shows a duct for an auxiliary power unit (APU) that is a classic example of three benefits of the investment casting process.

• This asymmetrical single-piece casting, with thick and thin wall sections and a cast-in grid pattern, provides a number of cast-in feature that improve product performance.

• Asingle piece that consolidates a number of details into a unitized casting streamlines manufacturing and paperwork tasks by significantly reducing part

count, production, and administrative steps. This is a common outcome of just about every conversion to the casting process.

• Combining single-piece simplicity with an asymmetrical configuration in a near-net shape, greduces raw-material input and machining requirements, and enables the production of a part that could not easily be produced by other means for the same cost or in the same short time frame. In the case of the APU duct, the design, which features a precise pattern of thick and thin sections and a strengthening grid pattern, optimizes the balance of strength and weight, producing a part perfectly suited to its application.

Intricate geometries

Intricate geometries are another feature of investment castings. Figure 2 shows a titanium fan frame. These are typically characterized by relatively large dimensions and extremely intricate
geometries. Fan frames are one of PCT’s specialties, and the organization has spent years developing techniques that maximize the benefits of investment casting. In addition to the benefits mentioned in regard to the APU duct, the investment casting process delivers a high “buy-to-fly” ratio. Because the casting process has achieved a high degree of precision, current production methods supply a near-net-shape casting that is extremely close to the dimensions of the finished piece. This capability accounts for the high buy-to-fly ratio, and also results in a piece that requires very little finish machining to prepare the component for subassembly. This feature of the process has a direct and positive impact on cost and manufacturing cycle time.

Part sets

Figure 3 shows investment cast titanium heat shields for commercial transports such as the Boeing 777. These components, which need to be produced in sets that are fitted together in subsequent assembly operations, offer an example of how precise the casting process has become. Heat shields are relatively large, asymmetrical pieces.Nonetheless, when produced in near-net configurations, they can be easily assembled to exacting tolerances, with excellent repeatability.In addition, thanks to process control enhancements over recent years, excellent surface finishes typically eliminate the need for coatings, thus shortening lead and cycle times.

New productdevelopment

Selection of the investment casting process can trigger a series of time- and money-saving steps, beginning at the earliest stages of the new-product-development (NPD) process. By encouraging product and casting designers to work collaboratively from the beginning, workable designs can be produced, tested, and certified in the shortest, most affordable manner. For example, PCT has worked with customers to develop and certify parts manufactured using SLA patterns. This

NPD strategy bypasses the need for expensive hard tooling before designs are finalized.

INVESTMENT CASTING

2009-02-01T22:15:00.000-08:00

Advances in investment casting over the past several years have enabled cost reductions and improved reliability in complex components.

Engineers are finding ways to bypass timeconsuming and expensive production
routes by investment casting hundreds of parts that were never cast before. Technological progress has improved control at every stage of the process, spurred alloy development, effectively exploited the considerable design freedom of the process, and leveraged the unique features of investment casting to enhance capability, repeatability, and affordability. Foundries have steadily reduced variability through the application of microprocessor controls, automated equipment, statistical methods, and scientific management techniques.

Investment Casting Process
The investment casting, or “lost-wax” process is a production method for making parts from molten metal. The process begins with the manufacture of a pattern that is the same shape as the end product. Usually made of wax formed in custom tooling, the individual pattern elements are joined to form a wax-pattern assembly. The assembly is repeatedly dipped into a ceramic slurry and coated with sand stucco to build up a shell, which is then dried. When the shell is dry, the assembly is placed in an autoclave and the wax is melted out. When empty, the mold is heated to the proper temperature and molten metal is poured into the mold. As the metal cools, it solidifies into a casting. Subsequently, the mold is broken off and the casting undergoes a number of finishing operations.

Solar-to-grid power system achieves 31.25% efficiency

2009-02-01T08:09:00.000-08:00

A new solar-to-grid system conversion efficiency record has been set by achieving a 31.25% net efficiency rate, compared with the previous record of 29.4%, report Sandia National Laboratories and Stirling Energy Systems. Conversion efficiency is calculated by measuring the net energy delivered to the grid and dividing it by the solar energy hitting the dish mirrors. The solar dish generates electricity by focusing the sun’s rays onto a receiver, which transmits the heat energy to a Stirling engine. The engine is a sealed system filled with hydrogen. As the gas heats and cools, its pressure rises and falls. The change in pressure drives the pistons inside the engine, producing mechanical power, which in turn drives a generator that makes electricity. The Stirling dishes are made with a low-iron glass with a silver backing that makes them highly reflective —focusing as much as 94% of the incident sunlight to the engine package, comparedwith prior efforts of about 91%. The mirror facets, patented by Sandia and Paneltec Corp. ofLafayette, Colo., are highly accurate and have minimal imperfections in shape.
For more information: Chris Burroughs, Sandia National Laboratories, Albuquerque, NM
87185; tel: 505/844-0948; coburro@sandia.gov; www.sandia.gov.

Metal organic frameworks bind and release hydrogen

2009-02-01T07:02:00.001-08:00

Metal-organic frameworks (MOFs) have been evaluated for hydrogen storage by a research team from NIST, the University of Maryland, and the California Institute of Technology. One of several classes of materials that can bind and release hydrogen under the right conditions, they have some distinct advantages over competitors. In principle they could be engineered so that refueling is as easy as pumping gas, and MOFs don’t require the high temperatures (110 to 500°C) some other materials need to release hydrogen. In particular, the team examined MOF-74, a porous crystalline powder developed at the University of California at Los Angeles. MOF-74 resembles a series of tightly packed straws comprised of mostly carbon atoms with columns of zinc ions running down the inside walls. Agram has about the same surface area as two basketball courts. The researchers used neutron scattering and gas adsorption techniques to determine that at 77K (–196°C, –320°F), MOF-74 can adsorb more hydrogen than any unpressurized framework structure studied to date — packing the molecules more densely than they would be if frozen in a block.

For more information: Dan A. Neumann, NIST, 100 Bureau Drive, Stop 6102, Gaithersburg,
MD 20899-6102; tel: 301/975-5252; dan.neumann@nist.gov; www.nist.gov.

Rare earth added to electrode reduces spatter in GMAW

2009-02-01T05:27:00.000-08:00

Atechnology called JFE Spray Transfer Arc (J-STAR) welding, in which a rare earth element is added to the electrode to reduce spatter, has been developed by JFE Steel, Tokyo, Japan. The conventional CO2 gas shielded arc welding process is carried out with an electrode-positive (EP) polarity. J-STAR welding, in contrast, requires the addition of an appropriate amount of rare earth element to the wire as an arc stabilizer, and the adoption of an electrode-negative mode reverse to the ordinary polarity. One feature of the arc phenomenon in the free transfer region of CO2 gasshielded arc welding is the increased arc concentration in the lower part of the droplet suspended from the leading end of the wire. In welding current over 250 A, a conical arc plasma was formed from the wire tip, and the droplets that transfer to molten pool became fine and continuous, what is called “spray transfer,” during J-STAR welding. In welding current under 200 A, application of waveform control of welding current achieved periodic short circuit transfer. As a result, spatter generation was reduced to less than 10% in comparison

with that of conventional CO2 gas shielded arc welding methods. For more information: Kataoka Tokihiko, JFE Steel, Tokyo, Japan; http:// www.jfe-steel.co.jp/en/research/report/ 010/pdf/010-07.pdf.

Nanomaterials show unexpected tensile strength under stress

2009-02-01T05:12:00.000-08:00

Materials such as silica that are brittle in bulk exhibit ductile behavior at the nanoscale, report researchers at the National Institute of Standards and Technology, Gaithersburg, Md. Computer simulations demonstrate the material extension and

necking that occurs during the separation of amorphous (top) and crystalline (bottom) silica nanoparticles. At the macroscale, the point at which a material fails or breaks depends on its ability to maintain its shape when stressed. The atoms of ductile substances are able to shuffle around and remain cohesive for much longer than their brittle cousins, which contain faint structural flaws that act as failure points under stress. However, at the nanoscale, these structural flaws do not exist, and hence the materials are nearly perfect. In addition, these objects are so small that most of the atoms that comprise them reside on the surface. The properties of the surface atoms, which are more mobile because they are not bounded on all sides, dominate at the nanoscale. This dominance gives an otherwise brittle material such as silica its counterintuitive fracture characteristics. For more information: Takumi Hawa, NIST, 100 Bureau Drive, Stop

8360, Gaithersburg, MD 20899-8360;

tel: 301/975-5235; takumi.hawa@nist.

gov; www.nist.gov.

Martensitic stainless has 10% better fatigue, 25% better impact

2009-02-01T05:04:00.000-08:00

A modification of AISI 420 martensitic stainless chromium strip steel with 10% higher fatigue resistance and 25% higher impact strength has reportedly been developed by Sandvik Steel, Sweden. Called Hiflex, it also has higher ductility and up to 10% improvement in bending fatigue strength compared with the best available competitive materials. The new steel is specifically designed for flapper valves, compressor components that are subjected to very high cyclic loads as the valve opens and shuts. Damping is the property that governs how quickly a flapper valve stops vibrating after impact, and high damping capacity contributes to high impact fatigue strength. Tests show that stress waves, which can lead to valve failure, decay or diminish more quickly in materials with high damping capacity. Sandvik Hiflex shows the highest damping capacity of all materials tested, suggesting the reason for its highest impact fatigue strength.

For more information: Sandvik Materials Technology, PO Box 1220, Scranton , PA18501; tel:

570/5850-7500; fax: 570/585-7513; www.smt.sandvik.com/nafta.

About Materials engineering

2009-01-31T11:19:00.000-08:00

Materials Engineering is a field of engineering that encompasses the spectrum of materials types and how to use them in manufacturing. Materials span the range: metals, ceramics, polymers (plastics), semiconductors, and combinations of materials called composites. We live in a world that is both dependent upon and limited by materials. Everything we see and use is made of materials: cars, airplanes, computers, refrigerators, microwave ovens, TVs, dishes, silverware, athletic equipment of all types, and even biomedical devices such as replacement joints and limbs. All of these require materials specifically tailored for their application. Specific properties are required that result from carefully selecting the materials and from controlling the manufacturing processes used to convert the basic materials into the final engineered product. Exciting new product developments frequently are possible only through new materials and/or processing.

Activities of materials engineers range from primary materials production, including recycling, through the design and development of new materials to the reliable and economical manufacturing for the final product. Such activities are found commonly in industries such as aerospace, transportation, electronics, energy conversion, and biomedical systems. The future will bring ever-increasing challenges and opportunities for new materials and better processing. Materials are evolving faster today than at any time in history. New and improved materials are an "underpinning technology" - one which can stimulate innovation and product improvement. High quality products result from improved processing and more emphasis will be placed on reclaiming and recycling. For these many reasons, most surveys name the materials field as one of the careers with excellent future opportunities.

U.S. Navy ship New York contains steel from ground zero

2009-01-31T10:23:00.000-08:00

With a bow fashioned in part with 7.5 tons of steel reclaimed from the wreckage of the World Trade Center, the Navy’s newest and perhaps most symbolic warship was christened on March 1 at Northrop Grumman Shipbuilding’s shipyard in Avondale, La. The San Antonio-clas amphibious transport dock ship is named the New York, a tribute to the victims of the terrorist attacks on Sept. 11, 2001. As crews cleaned up the World Trade Center site in lower Manhattan, large pieces of salvageable steel were loaded on flatbeds and delivered to a Gulf Coast foundry in Amite, La. There, it was melted and formed into a part of the ship’s bow stem, the foremost section of the hull on the water line. The 684-foot-long ship will be commissioned in New York in 2009 and based in Norfolk as part of the Atlantic Fleet.

For more information: Northrop Grumman Shipbuilding, Avondale, LA 70094;

www.ss.northropgrumman.com/christenings/NewYork; www.ussnewyork.com; www.navy.mil.

Die Cast Alloys

2009-01-30T20:15:00.000-08:00

Die Cast Alloys

CHANGES IN DIE CASTING ALLOY COMPOSITION CAN AFFECT THE PHYSICAL CHARACTERISTICS OF A FINISHED PART, RESULTING IN INCREASED STRENGTH OR IMPROVED THERMAL CONDUCTIVITY, OR THE ALLOY MAY BE MODIFIED TO IMPROVE PRODUCTION EFFICIENCY BY REDUCING DIE SOLDERING OR ALLOWING THINNER WALL CASTINGS. SPECIALTY ALLOYS MAY BE DEVELOPED TO MEET A SPECIFIC PRODUCT NEED, OR TO PROVIDE SOLUTIONS FOR A GENERAL SET OF INDUSTRY CRITERIA.

New alloys may even be developed to help keep markets for a particular metal. For example, as zinc prices have tripled, the industry has lost 250 tons of zinc castings, according to the International Lead Zinc Research Organization Inc. (ILZRO). To help mitigate this problem, ILZRO

and industry partners Stroh Die Casting, Brillcast, and Il Kaba are working on a new zinc alloy that is 40% more fluid, allowing thinner wall castings that retain the coating characteristics and other advantages of zinc. Since less material is used in the thin wall castings, the overall cost of zinc products can be reduced. Although the alloy is not yet ready for commercial introduction, Stroh has cast sample products with wall thicknesses

of 0.012 inch, leading to a 25% reduction in casting cost. Extensive research by the North American Die Casting Association (NADCA) and other partners has created a vast body of knowledge about aluminum alloys, and breakthroughs are being made with other metals. NADCA, in conjunction with Worcester Polytechnic Institute (WPI), has created I-Select Al software focused specifically on aluminum alloys. The I-Select Al software helps designers, product specifiers, and die casters identify the alloy chemistry needed to meet a specific set of casting properties, such as density, thermal conductivity, ultimate tensile strength, tensile yield strength, ductility, and elasticity.

ONGOING ALLOY RESEARCH

The development of I-Select-Al software is part of an ongoing research effort to define a set of premium grade alloys that are optimized for specific properties. The program, “Castings for Improved Readiness,” is being conducted by NADCA, WPI, the Defense Logistics Agency (DLA), and several industry partners that are testing alloys for various applications. One of the goals of the program is to meet industry and DLA needs for better procurement data to reduce lead

times while tailoring the alloy composition to ensure cost-effective, highquality parts. This data for optimized alloys is essential because current chemistry specification limits are wide, resulting in

large variations in mechanical properties and leading to non-compliance issues. The program is

examining a total of 36 alloy formulations. Two of the alloys have been selected for trials with die cast military parts that are already in production. Twin City Die Castings Company and Premier Tool and Die Casting are industry partners in this effort. Casting samples are being analyzed at WPI to delineate the specific performance characteristics that need to be optimized via microstructural control. As these properties are defined, they will be included in new specification standards, which should be completed by the first quarter of 2008.