Solidification Behavior and Microstructures Characteristics of Ti-48Al-3Nb-1.5Ta Powder Produced by Supreme-Speed Plasma Rotating Electrode Process

In this study, the characteristics and solidification behavior of Ti-48Al-3Nb-1.5Ta powder produced by supreme-speed plasma rotating electrode process (SS-PREP (R)) were investigated. The microstructure, phase and characteristics were analyzed by scanning electron microscopy, X-ray diffraction and other methods. The atomization mechanism is direct drop formation. 3 The relationship between the particle size and cooling rate is v(c) = 3.14 x 10(-7) . d(-2) + 1.18 x 10(-2) . d(-3/2), and the relationship between secondary dendrite arm space and the particle size is lambda = 0.028d + 0.11 , as well as the relationship between SDAS and cooling rate is lambda = 4.84 x 10(5) . T-1.43. With increase in particle size, the surface structure gradually changes from the featureless smooth structure to dendritic and cellular dendritic morphology, and the flow ability becomes better. The carbides mainly exist within 5 nm of the surface and the oxidation layer is about 20 nm thick. Ti-48Al-3Nb-1.5Ta powder was mainly composed of alpha(2) phase and gamma phase. With increase in particle size, the content of gamma phase increases, and the hardness decreases accordingly. The 106-250 p.m particles are composed of multiple grains with the grain size of 70-80 mu m. The microstructure, phase composition and hardness of different TiAl powders with the same size are similar, but the elastic modulus is different.