Cavitation failure in superplastic alloys

Abstract

While all superplastically formable (SPF) alloys cavitate during deformation, it has been noted that excessive cavitation may result in either undesirable postforming characteristics of premature failure. Attention is presently given to theories for the nucleation, growth, and interlinkage of cavities in SPF alloys, as well as to experimental data relevant to these theories' assessment. The superposition of hydrostatic pressure is found to diminish the degree of cavitation, and pressures of the order of the flow stress are found to eliminate cavitation. The reduction of an SPF alloy's grain boundary particle sizes to a lower-than- critical value, and the development of boundary particles that maintain either fully coherent or semicoherent interfaces with their matrix, are also capable of reducing cavitation. (O.C.)