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

Ternary Sn-Ni-V alloys were prepared and annealed at 980A degrees C, 600A degrees C, and 300A degrees 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 980A degrees C was studied. Nine three-phase regions and more than 20 conjugate lines were detected at 980A degrees C. The range of composition of VNi2Sn at 980A degrees 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 600A degrees C and 300A degrees C was also investigated experimentally. The solubility of Ni in VSn2 and V in Ni3Sn4 at 600A degrees C and 300A degrees C are both less than 0.5 at.%.