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Carpenter A.J.,University of Texas at Austin | Barnes A.J.,Superform United States | Taleff E.M.,University of Texas at Austin
Materials Science Forum | Year: 2013

Complex sheet metal components can be formed from lightweight aluminum and magnesium sheet alloys using superplastic forming technologies. Superplastic forming typically takes advantage of the high strain-rate sensitivity characteristic of grain-boundary-sliding (GBS) creep to obtain significant ductility at high temperatures. However, GBS creep requires fine-grained materials, which can be expensive and difficult to manufacture. An alternative is provided by materials that exhibit solute-drag (SD) creep, a mechanism that also produces elevated values of strain-rate sensitivity. SD creep typically operates at lower temperatures and faster strain rates than does GBS creep. Unlike GBS creep, solute-drag creep does not require a fine, stable grain size. Previous work by Boissière et al. [1] suggested that the Mg-Y-Nd alloy, essentially WE43, deforms by SD creep at temperatures near 400°C. The present investigation examines both tensile and biaxial deformation behavior of Elektron™ 43 sheet, which has a composition similar to WE43, at temperatures ranging from 400 to 500°C. Data are presented that provide additional evidence for SD creep in Elektron 43 and demonstrate the remarkable degree of biaxial strain possible under this regime (>1000%). These results indicate an excellent potential for producing complex 3-D parts, via superplastic forming, using this particular heat-treatable Mg alloy. © (2013) Trans Tech Publications, Switzerland. Source


Barnes A.J.,Superform United States | Stowell M.J.,University of Cambridge | Grimes R.,University of Warwick
Key Engineering Materials | Year: 2010

Prior to 1969 the pioneering work carried out by Backofen and Fields in the USA and Johnson and Hundy in the UK demonstrated the 'promise' of Superplastic Forming. Using fine grained dual phase alloys, typically of eutectic or eutectoid compositions, they produced some of the very first superplastically formed prototype components. Although not always 'practical', these dual phase alloys were stable when heated and if appropriately processed often proved to be very superplastic. At that time 'dilute' alloys, including the majority of commercial aluminum alloys, having only a small volume fraction of alloying additions, were thought not to be capable of superplastic behavior due to their propensity to grain coarsen when heated. Breakthrough came in 1969 when at the research labs of Tube Investments, Hinxton Hall Nr Cambridge UK; the first 'SUPRAL' type dilute superplastic aluminum alloys were created. This paper describes the events and 'science' that led up to this development and the remarkable technology that has emerged since the authors began their superplasticity careers more than forty years ago. The future direction that this intriguing technology is likely to take is also explored. © (2010) Trans Tech Publications. Source


Barnes A.J.,Superform United States
Journal of Materials Engineering and Performance | Year: 2013

In late 1964 Backofen, Turner & Avery, at MIT, published a paper in whieh they deseribed the "extraordinary formability" exhibited when fine-grain zinc-aluminum euteetoid (Zn 22 Al) was subjected to bulge testing under appropriate conditions. They concluded their research findings with the following insightful comment "even more appealing is the thought of applying to superplastie metals forming techniques borrowed from polymer and glass processing," Since then their insightful thought has become a substantial reality with thousands of" tons of" metallic sheet materials now being superplastically formed each year. This paper reviews the significant advances that have taken place over the past 40 years including alloy developments, improved forming techniques and equipment, and an ever increasing number of commercial applications. Current and likely future trends are discussed including; applications in the aerospace and automotive markets, faster-forming techniques to improve productivity, the increasing importance of computer modeling and simulation in tool design and process optimization and new alloy developments including super plastic magnesium alloys. © 2013 ASM International. Source


Raman H.,Superform United States | Barnes A.J.,Superform United States
Journal of Materials Engineering and Performance | Year: 2010

Over the past thirty years Superform has been a pioneer in the SPF arena, having developed a keen understanding of the process and a range of unique forming techniques to meet varying market needs. Superform's high-profile list of customers includes Boeing, Airbus, Aston Martin, Ford, and Rolls Royce. One of the more recent additions to Superform's technical know-how is finite element modeling and simulation. Finite element modeling is a powerful numerical technique which when applied to SPF provides a host of benefits including accurate prediction of strain levels in a part, presence of wrinkles and predicting pressure cycles optimized for time and part thickness. This paper outlines a brief history of finite element modeling applied to SPF and then reviews some of the modeling tools and techniques that Superform have applied and continue to do so to successfully superplastically form complex-shaped parts. The advantages of employing modeling at the design stage are discussed and illustrated with real-world examples. © ASM International. Source


Schroers J.,Yale University | Hodges T.M.,Yale University | Kumar G.,Yale University | Raman H.,Superform United States | And 3 more authors.
Materials Today | Year: 2011

While plastics have revolutionized industrial design due to their versatile processability, their relatively low strength has hampered their use in structural components. On the other hand, while metals are the basis for strong structural components, the geometries into which they can be processed are rather limited. The "ideal" material would offer a desirable combination of superior structural properties and the ability to be precision (net) shaped into complex geometries. Here we show that bulk metallic glasses (BMGs), which have superior mechanical properties, can be blow molded like plastics. The key to the enhanced processability of BMG formers is their amenability to thermoplastic forming. This allows complex BMG structures, some of which cannot be produced using any other metal process, to be net shaped precisely. © 2011 Elsevier Ltd. Source

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