Fabrication of the DO22-type intermetallic compound Al3Ta via powder metallurgy processes and its characterization

The ordered b.c.t. DO22-type intermetallic compound Al3Ta is difficult to fabricate homogeneously via conventional alloying methods owing to the different physical properties (density and melting and boiling points) of the component elements. Three powder metallurgy methods were used in this work, and hot isostatic pressing was found to be a good means of fabricating the compound. Hot isostatically pressed powders became almost a single-phase DO22-type compound of Al3Ta with a small fraction of a second phase formed incoherently inside the grains. The compound fractured at room temperature revealed a cleavage transgranular mode in regions where the grain size is large and an intergranular mode in regions where it is smaller than around 2 μm. The compound slightly deformed at room temperature showed perfect superlattice dislocations lying on (111)f.c.c. whose Burgers vectors are of the [11¯0] and 1/2 [1¯1¯2] types.