Mechanism of high strain rate superplasticity in aluminium alloy composites

A constitutive equation has been obtained through an analysis of high strain rate superplasticity (HSRS) data on a 2124 Al-Si-N-3(4) composite. The parametric dependencies of HSRS in composites are different from those observed in conventional aluminium alloys and mechanically alloyed alloys. The HSRS in composites exhibits high activation energy values of 293-338 kJ mol(-1) and an inverse grain size and reinforcement size dependence. It is suggested that the mechanism of HSRS in composites is ''interface controlled'' superplasticity. This is depicted on a new ''superplasticity mechanism map for composites''. The map can be used as a guideline for designing composites for optimum superplasticity. Copyright (C)1997 Acta Metallurgica Inc.