The structure and fracture mode of rapidly solidified Pt₃Ga

This paper reports a study of the structure and fracture mode of Pt₃Ga. The results show that the structure of this compound is a tetragonal distortion of the L1₂ structure with lattice parameters of a = 5.47 Å and c = 7.89 Å. If the gallium concentration decreases from 22.8 at.% to 21.5 at.%, a disordered face-centered cubic phase also forms. This phase is Pt-rich and appears to form along the grain boundaries of the Pt₃Ga phase. The fcc phase can also contain coherent Pt₃Ga precipitates. Single phase Pt₃Ga fails in a very brittle manner, and the fracture mode is intergranular. Boron additions have no effect on the fracture mode, since boron does not segregate to the grain boundaries. The fracture of an alloy containing a small amount of the disordered fcc phase is also brittle, but the fracture mode is predominantly transgranular.