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

Abstract

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.

Keywords

• mechanical milling
• anomalous N-Sn eutectic
• solid state transformation