Microstructure evolution of Ti-47Al-2Cr-2Nb alloy in the liquid-metal-cooling (LMC) directional-solidification process

Abstract

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.

Keywords

TiAl-based alloy / directional solidification / lamellar orientation / peritectic reaction

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