Effect of Cooling Rate on Powder Characteristics and Microstructural Evolution of Gas Atomized β-Solidifying γ-TiAl Alloy Powder

Abstract

The gas atomization is a production technique of a metallic powder. In this study, the β-solidifying Ti-44Al-6Nb-1.2Cr alloy powder fabricated by gas-atomization was investigated regarding the evolving shape, phase constitution, and chemical distribution as a result of the high solidification rate. The powder showed a spherical shape regardless of its size, indicating no relation of solidification rate to powder shape. However, the small powder (D 50 = 36.0 µm) showed less segregation and was composed of β and α 2 dual phases. Whereas, the large powder (D 50 = 78.7 µm) is relatively high segregation and composed of almost a single α 2 phase because of the difference in the cooling rates. The findings obtained here demonstrated the understanding of phase transformation during the rapid solidification and continuous microstructural evolution process in the β-solidifying alloy.