Effect of temperature gradient on competitive growth behavior of Si and YSi₂ in a Si–Y eutectic alloy prepared by Bridgeman method

The Si–Y eutectic alloy has been prepared by Bridgeman method where the high temperature gradient (G_E) can be obtained by means of double heating combining with liquid metal cooling. The microstructures of longitudinal section and cross section at different G_E have been observed. It can be seen clearly that the YSi₂ phase presents the evolution process of thick banded shape, island shape, reticular shape and fine strip shape as G_E increases from 90 K/cm to 200 K/cm. Based on the interface growth temperature model, it can be concluded that the interface growth temperatures of Si phase and YSi₂ phase both will decrease linearly with increasing G_E while that of eutectic structure will keep a constant of 1485.6 K. Two critical temperature gradients G_EC1 = 52 K/cm and G_EC2 = 111 K/cm have been calculated. Eutectic coupling growth will take the dominant position when the actual G_E is greater than G_EC2. The primary Si phase will begin to form as G_E is smaller than G_EC2 and will be thicker as G_E is smaller than G_EC1. The coupling effect of withdrawal rate and G_E on the microstructures of the Si–Y alloy also has been analyzed comprehensively.