Phase Equilibria of the Sn–Ni–V System: The 980°C Isothermal Section and the Sn-Rich Corner at 600°C and 300°C

Ternary Sn–Ni–V alloys were prepared and annealed at 980°C, 600°C, and 300°C for 15, 60 and 60 days, respectively. The annealed alloys were metallographically examined and the equilibrium phases formed were identified on the basis of determination of composition and x-ray diffraction analysis. The isothermal region of the ternary Sn–Ni–V system at 980°C was studied. Nine three-phase regions and more than 20 conjugate lines were detected at 980°C. The range of composition of VNi2Sn at 980°C spans 24.5–59.2 at.% V, 52.1–25.5 at.% Ni, and 15.3–23.4 at.% Sn. Its lattice constant increases with increasing V content. A sharp increase near 40.4 at.% V is indicative of a second-order transition. It is believed that atomic site occupation changed when the V content was >40.4 at.%. The maximum solubility of V in Ni3Sn2 can reach 23.3 at.%; that in Ni3Sn is below 0.6 at.%. Up to 3.4 at.% Ni dissolves in V3Sn. The Sn-rich corner of the Sn–Ni–V system at 600°C and 300°C was also investigated experimentally. The solubility of Ni in VSn2 and V in Ni3Sn4 at 600°C and 300°C are both less than 0.5 at.%.