Superplastic forming is a specialized procedure for deforming metal sheets to exceptionally large plastic stresses to generate thin-walled, near-net-shaped components. You can know more about superplastic forming via Macrodyne Technologies.
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Superplastic forming allows for greater stretching of sheets than rolling or sheet forming. The sheet is then placed in a die cavity. High gas pressure is evenly applied to heat the metal and plastically deform it at large strains. This creates a single-piece, complex-shaped component.
Many variations are depending on the shape of the part. Superplastic deformation results in a uniformly thinned metal over the whole part. This is not accompanied by necking or local thinning, which can often lead to tensile cracks. Another common reason for tensile failure is that the material doesn't develop cavities during its forming.
Superplastic forming can only be used on metals that have very high levels of plasticity. Superplastic metals have fine, equiaxed grains that are typically less than 10-20mm.
The grain structure must remain stable at high temperatures during superplastic forming. This is often accomplished by dispersing thermally stable metal particles.
These particles pin grain boundaries, preserving the fine grain structure at high temperatures. They also provide high resistance to cavitation (void creation). These properties make metals superplastic at high temperatures, usually one-half their absolute melting temperature.
Superplastic forming is slower than conventional alloys and has higher material costs.