Phase equilibria and martensitic and magnetic phase transformations of theβ phase in the Co-Ni-Ga system have been investigated. It has been shown that the β phase is in equilibrium with the α-phase over a wide range compositions at 600-1100°C. The β phase exhibits both a paramagnetic-ferromagnetic transition and a thermoelastic martensitic transition from B2 to L10 structure. The Curie temperature T C increases with decreases in both Ni and Ga content, and the martensitic transition starting temperature Ms decreases with decreasing Ni content and with increasing Ga content. The composition region of the β phase exhibiting the thermoelatstic martensitic transformation from ferromagnetic austenite is located near the a + β two-phase region. T C and s of α + β two-phase alloys increase with increasing annealing temperature.
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