Effects of Sn addition on dynamic grain growth in a binary Mg-1Ca alloy

The possibility of dynamic grain growth of a binary Mg-1Ca alloy with minor tin contents was investigated at various conditions of temperature and strain rate. Mg-1Ca, Mg-1Ca-1Sn and Mg-1Ca-2Sn alloys were cast and homogenized at 410 °C followed by hot-rolling at 400 °C with equal strains. Calcium contributed to refining of grains, with an additional support from tin. In the as-cast alloys, tin was found to promote dendrite formation. Though presence of Ca 2 Sn phase was predicted by thermodynamic modelling, microstructurally a ternary phase MgCaSn was predominantly found. This ternary phase was also comparatively coarser in size. Uniaxial tensile test of rolled samples was carried out at temperatures 300, 350, 400 and 450 °C, and at two different strain rates 5 × 10 −4 s −1 and 1 ×  10 − 4 s − 1 . Variation of grain distribution was also measured at the grip and gauge regions at different locations. Samples were taken from six different locations of the deformed samples. Even at faster deformation, the grains were not elongated. At slower strain rate condition, extent of dynamic grain growth was higher compared to that of the higher strain rate condition. Mg 2 Ca particles were not effective in restricting movement of grain boundaries. Mg 2 Sn particles were dissolved in the matrix at the elevated temperatures, and the grain growth limiting was profoundly dominated by the presence of MgCaSn phase.