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

Abstract

Abstract The Si–Y eutectic alloy has been prepared by Bridgeman method where the high temperature gradient (GE) can be obtained by means of double heating combining with liquid metal cooling. The microstructures of longitudinal section and cross section at different GE 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 GE 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 GE while that of eutectic structure will keep a constant of 1485.6 K. Two critical temperature gradients GEC1 = 52 K/cm and GEC2 = 111 K/cm have been calculated. Eutectic coupling growth will take the dominant position when the actual GE is greater than GEC2. The primary Si phase will begin to form as GE is smaller than GEC2 and will be thicker as GE is smaller than GEC1. The coupling effect of withdrawal rate and GE on the microstructures of the Si–Y alloy also has been analyzed comprehensively.