SUPERPLASTIC INDENTATION CREEP OF FINE-GRAINED Sn-1% Bi ALLOY

Abstract

Creep and superplasticity of the fine-grained Sn -1wt.% Bi alloy, processed by conventional rolling (CNR), cryorolling (CRR) and equal channel angular pressing (ECAP) routes, were investigated by indentation testing at room temperature (T > 0.6T m ). Based on the steady-state power law creep relationship, the stress exponents of 4.1, 2.8 and 2.5 were obtained for the CNR, CRR and ECAP routes, respectively. The corresponding strain rate sensitivity (SRS) indices of 0.24, 0.36 and 0.40, corresponding respectively to the grain sizes of 2.8, 2.1 and 1.2 μm, indicate that the materials processed by ECAP and CRR exhibit superplastic deformation behavior for which, grain boundary sliding is the possible creep mechanism.