Influence of Ni on stability of martensitic transformation in Zr ₅₀Cu_50-xNi_x

Influence of Ni content on the stability of martensitic transformation and microstructure evolution was investigated in Zr₅₀Cu _50-xNi_x (x = 0, 5, 10, 15). Microstructural observations revealed that the both B19′ and Cm martensites were present in all the alloys investigated. The thermal behaviors results indicated that the initial M_s increased from 433 K to 699 K with an increase of Ni content from 5 to 15 mol.%. For x = 5, the forward and reverse martensitic transformation disappeared after thermal cycling. For x = 10 and 15, both transformation still remained even after 10 cycles. Two-step transformation behaviors were observed on both forward and reverse transformation in x = 15 alloy. Ni addition decreased the transformation hysteresis. Microstructural observations revealed the Ni addition up to 10 mol.% suppressed the decomposition of ZrCu into Zr ₂Cu and τ₅ phases during 10 thermal cycling treatments. These results indicated that the addition of Ni over 10 mol.% stabilized the martensitic transformation during thermal cycling.