Sheet Thermoforming of a Superplastic Alloy

Ordinary metals and alloys have not heretofore been shaped by the sheet thermoforming techniques so advantageously used by the plastics industry. Although a polymeric material may undergo a manifold increase in surface area during vacuum or pressure forming, metal or alloy sheet invariably fails by localized deformation and thinning at relatively low strains when subjected to tensile plastic deformation. Recent reports of “superplastic” behavior in metals and alloys
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include examples of extraordinary amounts of uniform tensile elongation. This communication reports the initial results of efforts to utilize a superplastic alloy in a laboratory vacuum-forming operation.