Microstructure and Impression Creep Behaviour of Mg-Sb Alloys

Abstract

The microstructure and detailed impression creep behaviour of the Mg-Sb (Sb = 1.0, 1.4, 1.8 (wt.%)) alloys have been investigated. All the Mg-Sb alloys consist of pure Mg and continuous network of Mg3Sb2 phase. The volume fraction of the Mg3Sb2 phase increases with increase in Sb content in the alloys. The impression creep experiments are carried out in the temperature range of 150 to 200oC and stress range of 150 to 300 MPa by impressing a cylindrical indenter on the surface of specimen. All the creep results exhibit a well-defined primary creep followed by secondary (steady state) creep. Tertiary stage is missing in all the plots owing to the compressive nature of the tests. The impression velocity decreases with increase in Sb content owing to increased Mg3Sb2 content following Sb addition. The Mg-1.8Sb alloy exhibited the best creep resistance among the alloys developed. The values of stress exponent (n) vary from 5.9 to 6.5 and the values of activation energy (Q) vary from 66.6 to 79.3 kJ/mol, which confirms dislocation climb controlled by pipe diffusion is the dominant creep mechanism in all the Mg-Sb alloys in the temperature and stress levels employed. Three distinct deformation zones were observed below indentation and the extent of deformation decreases with increasing Sb content.