Solid state transformation of non-equilibrium Ni-Sn powder with a eutectic composition

Solid state transformation of supersaturated solid solution to anomalous Ni-Sn eutectic has been studied. The metastableNi-Sn solid solution was prepared via mechanical alloying of a mixed Ni+Sn powder containing 32.5 wt-% Sn powder.The milling conditions included ball to powder ratio (BPR) of 5:1 and milling speed of 300 rpm. Milling times were varied as5, 15, and 25 hours. Milling the mixed powder for longer than 15 hours resulted in formation of supersaturated Ni-Sn solidsolution. Differential thermal analysis of the supersaturated Ni-Sn solid solution revealed two reactions, namely peritectoidand peritectic reactions, occurring at 945 and 1,141°C, respectively. Heating of the supersaturated Ni-Sn solid solution todifferent temperatures such as 800, 850, 900, 950, 1,100, and 1,140°C with holding time of 10 minutes resulted in developmentof anomalous eutectic with Ni3Sn phase matrix embedded with Ni solution particles. Sintering and coarsening of the eutecticwas depending on heating temperatures