Analysis of void growth in superplastic materials

A number of materials is subject to the cavitation during superplastic deformation. The cavities nucleate at sites such as grain boundaries,second phase particles, and triple points; subsequently, they grow and interlink with the neighbouring cavities. Cavitation usually leads either to the undesirable post-forming characteristics or to the premature tensile failure. It is also apparent that the cavities can pre-exist in the form of cracks and decohered interfaces, which develop during thermomechanical processing necessary to produce the superplastic microstructures. Evidently, extensive cavitation imposes significant limitations on their commercial application. The effect of material properties such as the cavity growth rate of intentionally pre-machined voids on specimens subject to the tensile deformation and to the biaxial deformation has been determined. The tensile tests have been conducted at constant crosshead velocity, using a fine-grained Pb–Sn alloy that presents superplastic properties at room temperature. The results of the experiments are in agreement with the numerical predictions obtained using a code based on the finite element method (FEM).