Hot workability characteristics of cast and homogenized Mg–3Sn–1Ca alloy

Abstract

Hot working behavior of Mg–3Sn–1Ca alloy has been evaluated with a view to explore its potential as a wrought alloy. The temperature and strain rate dependence of steady state flow stress has been analyzed. The processing maps exhibited two domains both in the temperature range 350-550°C with one in the lower strain rate range (0.0003–0.01 s^-1) and the other at higher strain rates (1–10 s^-1). The apparent activation energies estimated in these two domains respectively are 217 kJ/mole and 154 kJ/mole. The activation area values obtained, after making a correction for the back-stress generated by the hard intermetallic CaMgSn particles, are in the range 13-100 b² and decreased with increasing effective stress. The corrected results suggest that the lower strain rate domain is controlled by lattice self-diffusion and grain boundary diffusion occurs at higher strain rates. Extrusion at 500°C and at a speed that corresponds to an average strain rate of 3 s^-1 yielded a sound product with a dynamically recrystallized microstructure.