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The unusual ability of some metals and alloys to elongate uniformly by thousands of percent at elevated temperatures, much like hot polymers or glasses.


The unusual ability of some metals and alloys to elongate uniformly thousands of percent at elevated temperatures, much like hot polymers or glasses. Under normal creep conditions, conventional alloys do not stretch uniformly, but form a necked-down region and then fracture after elongations of only 100% or less. The most important requirements for obtaining superplastic behavior include a very small metal grain size, a well-rounded (equiaxed) grain shape, a deformation temperature greater than one-half the melting point, and a slow deformation rate. See Alloy, Creep (materials), Eutectics

Superplasticity is important to technology primarily because large amounts of deformation can be produced under low loads. Thus, conventional metal-shaping processes (for example, rolling, forging, and extrusion) can be conducted with smaller, and cheaper equipment. Nonconventional forming methods can also be used; for instance, vacuum-forming techniques, borrowed from the plastics industry, have been applied to sheet metal to form car panels, refrigerator door linings, and TV chassis parts. See Metal forming

References in periodicals archive ?
Industrial know-how has historically been the tool of choice to define the superplastic forming process but, by using the most up-to-date material testing, finite element modelling and process methods, the research centre is able to achieve optimal output.
The constitutive equation of superplastic deformation at relatively low temperature abides to viscoplastic Equation (2) proposed by Rossard, which indicates that the process combines strain hardening with strain rate hardening.
A research study examining the superplastic behavior of a fine-grained (~2 [micro]m) WE43 magnesium alloy containing spherical precipitates (~200 nm) within grains revealed a super plasticity with an elongation to-failure of over 1000 percent at 400[degrees]C.
and Lu, K., "Superplastic Extensibility of Nanocrystalline Copper at Room Temperature," Science, 287(5457): 1463- 1466(2006).
The articles that make up the main body of the text are organized in five chapters devoted to the mechanisms of superplasticity, superplastic materials, microstructure refinement, industrial applications, and other related subjects.
Zr[O.sub.2] has many interesting characteristics, such as superior mechanical characteristics, increased fracture toughness, hardness, strength, high thermal expansion coefficient, low thermal conductivity, superplastic deformation, phase stability, and good chemical resistance, which have resulted in a variety of industrial and engineering applications that include high durability coating, catalytic agents, medical prosthetics, cutting tools, synthetic jewels, high density grinding media, wear components, bearings, seals, valves, nose cones and tiles for space shuttles and missiles, turbines, and the most demanding aviation engines [12-17].
Nitinol SE (Nitinol Super Elastic) wires are superplastic. They have a pure shape memory and are highly sensitive to changes in temperature affecting their mechanical properties [37], but in vivo they do not have a thermoelastic shape memory [9].
The other 66 papers cover processes, process and production planning, presses and press tools, materials and testing, modeling techniques, cutting and joining, microtechnologies, quality and reliability, manufacturing systems, a case study of extending the value-stream-mapping approach to the comprehensive design of a lean sheet metal manufacturing system, analyzing the electric energy consumption in single-point incremental forming processes, and developments in monitoring die condition during superplastic forming.
His work on superplastic forming and friction stir processing of lightweight alloys, particularly magnesium alloys, is well recognized and has been published in the finest international journals and conference proceedings.
Ono, "Attenuation measurement of Laser excited So-Lamb wave by the wavelet transform and porosity estimation in superplastic Al-Mg plate", Hihakaikensa (Nondestructive Testing), vol.