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

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

Hot working parameters and mechanisms in as-cast Mg–3Sn–1Ca alloy

The hot working characteristics of as-cast Mg–3Sn–1Ca alloy have been studied using processing-map technique and the kinetic rate equation. The map exhibited two domains; one in the lower strain rate range (0.0003-0.01 s-1) and the other in the higher strain rate range (0.1-10 s-1)-both falling in the same temperature range of 350–550 s-1. Hot extrusion at 500°C and a speed corresponding to an average strain rate of 3 s-1 exhibited dynamically recrystallized microstructure. The estimated apparent activation energy values are higher than those for self-diffusion in pure magnesium suggesting that the large volume fraction of MgSnCa intermetallic particles causes significant back stress

Optimum parameters and rate-controlling mechanisms for hot working of extruded Mg–3Sn–1Ca alloy

The hot working behavior of extruded Mg–3Sn–1Ca alloy has been characterized by compression testing in the temperature range of 300–550°C and strain rate range of 0.0003–10 s−1 with a view to evaluate the optimum processing parameters as well as the rate-controlling mechanisms. Processing maps, developed on the basis of the temperature and strain rate dependence of flow stress, exhibited two domains in which dynamic recrystallization occurs. Both these are in the temperature range 325–500°C, with one in the lower strain rate range (0.0003–0.003 s−1) and the other in the higher strain rate range (1–10 s−1), the optimum temperature being 400°C. Kinetic analysis in the above two domains yielded apparent activation energy values of 196 and 168 kJ/mole, respectively, which are higher than that for self-diffusion in pure magnesium suggesting that the large volume fraction of CaMgSn intermetallic particles in the matrix causes significant back stress. In the change-over strain rate range (0.003–0.3 s−1), unusual grain size changes have occurred which may render microstructural control difficult