Microstructure Evolution of Ti-47Al-2Cr-2Nb Alloy in the Liquid-Metal-Cooling （LMC） Directional-Solidification Process

The microstructure evolution of Ti-47Al-2Cr-2Nb alloy was investigated on liquid metal cooling type directional solidified apparatus at high temperature gradient.The analysis shows that it is solidified with primary β cells/dendrites,and then α phase is formed through peritectic reaction.Once the columnar grains grow into the steady state,the lamellar orientation inclined with the angle of 45° to the withdrawal direction is more favored than that with parallel to the withdrawal direction.In addition,α phase grain nucleates from β-interdendrite regions,and grows up to the dendritic trunk.If no other α grain hinders its growth,it would occupy the whole dendrite,or it would stop at the dendritic trunk for the weakened motivating drive in the β dendritic core.