Solidification characteristics of TiAl powders produced by plasma rotating electrode process

The impurity levels, shapes and solidification characteristics of PREPed Ti-51at% Al powders were investigated. Oxygen and carbon contents were varied very much with particle with particle size. The appearances and microstructures of powders were found to be depended on cooling rate which is in turn particle size. The estimated cooling rate of powders ranging 200 to 50μm in size was 1.6x104 - 1.7x105 K/s. The coarse powders were solidified as primary α dendrite. From about 30% of ∼ 50μm in size martensite-like microstructure was found, which was believed to result from the solid state transformation of primary β phases during cooling. (Author)