Microstructural characterisation of a gas atomised Ti6A14VTiC composite

Abstract

Gas atomization is a well established process for producing rapidly solidified powders from superalloys, high alloy steels and aluminium alloys, and it has been applied to produce titanium alloy powders. Compared with other rapid solidification techniques, such as melt spinning and melt overflow, the cooling rate of gas atomization is low, being 10[sup 2]--10[sup 3] Ks[sup [minus]1], which might sacrifice some features of rapid solidification processing. However, its production capacity is substantial and it has an industrial potential. In early studies, titanium-based TiC particulate composites were prepared via powder or casting routes. In the composites fabricated via powder routes, the TiC reinforcement is equiaxed particles and their size is dependant upon the original TiC powder which is usually larger than 5 [mu]m. In cast composites TiC is dendritic. TiC dendrites are usually coarse, since the cooling rate is limited by the ingot size. Melt spinning was successfully used to produce very small TiC particles, less than 0.3 [mu]m, in the composites containing TiC up to 25 vol%. However, the industrial application of melt spinning for production of composites is unlikely, but a combination of gas atomization and powder metallurgy could be used. An investigation on the microstructural characteristics of themore » gas atomized Ti6Al4V-20vol%TiC composite powders and the HIPped bulk composite is presented in this paper.« less