Phase transformation behavior of Cu-10Ni-3Al-0.8Si alloy

Abstract

Microstructure evolution of solution treated Cu-10Ni-3Al-0.8Si alloy aged at different temperatures was investigated and different transformation products were observed: modulated structure resulting from spinodal decomposition, L12 ordering of matrix, continuous Ni3Al precipitates, continuous δ-Ni2Si precipitates and discontinuous precipitates. Modulated structure, L12 ordering of matrix and micro-twins formed initially at 450 °C, while continuous Ni3Al and δ-Ni2Si particles precipitated soon. Increasing temperature led to the formation of discontinuous precipitates, dissolution of Ni3Al and cellular decomposition. The alloy showed excellent over-aging resistance at 450 °C because the Ni3Al and δ-Ni2Si precipitates grew very slowly and the addition of silicon hindered the precipitation of the coarsening NiAl phase