Pre-primary phase formation in solidification of nickel-aluminium bronze

Abstract

The sequence of phase formation through the solidification range of BS 1400: AB2 nickel-aluminium bronze has been studied using both a controlled unidirectional solidification technique and isothermal treatments. Two different forms of iron-rich k₁-phase were seen to be precipitated from the liquid at above the liquidus temperature for the primary copper-based solid solution. One of these forms k₁-phase was shown to be a strong nucleant for the primary solid solution, and is therefore a potent grain refiner. The amounts and formation temperatures of these pre-primary k₁-phases were seen to depend on alloy composition within the AB₂ specification range.