The morphology, crystallography, and chemistry of phases in as-cast nickel-aluminum bronze

Abstract

The morphology, crystallography, and composition of the phases present in as-cast nickel-aluminum bronze of nominal composition copper-10 wt pct aluminum-5 wt pct nickel-5 wt pct iron have been investigated using optical, electron optical, and microprobe analysis techniques. The as-cast microstructure consists of copper-rich α, martensitic β, and κ-phases based on Fe₃Al and NiAl. The κ_z precipitates have a dendritic morphology and are cored; the composition ranges from iron-rich solid solution to Fe₃Al. The κ_II and κ_iv precipitates have, respectively, a dendritic and an equiaxed/dendritic morphology, and are based on Fe₃Al, while κ_III is a eutectoidal decomposition product of lamellar or globular morphology based on NiAl. The κ_I, κ_II, and κ_III precipitates have the Kurdjumov-Sachs orientation relationship with α matrix. Small κ_IV precipitates exhibit the Nishiyama-Wasserman orientation relationship with the α matrix, while large κ_iv precipitates have an orientation relationship which lies between Kurdjumov-Sachs and Nishiyama-Wasserman.