Phase equilibria in the Ni-Co-Ga alloy system

Phase equilibria among the α (A1), α′ (L12), β (B2), δ (Ni5Ga3) and ɛ (Ni13Ga9) phases at elevated temperatures and the existing composition region of the martensite phase at room temperature in the Ni-Co side of the Ni-Co-Ga system were examined by electron probe microanalysis (EPMA) using diffusion triples which were fabricated by two-step diffusion coupling. It was confirmed that single-phase regions of the α, α′ and β phases at 700 and 1000 °C exist in a wide composition range parallel to Ni-Co section and that the existing region of the martensite phase at room temperature is also located over a wide range in the β phase along the β + α (or α′) two-phase region.