Effect of aging temperature on microstructure and properties of cold-rolled Cu-Ni-Si alloy

Abstract

The aging process plays a pivotal role in shaping the microstructure of Cu-Ni-Si alloys, a typical kind of precipitation-strengthened Cu alloy. This process significantly affects both the mechanical and electrical properties of the final Cu alloy strips. In this study, Cu-Ni-Si alloy sheets underwent a 90 % reduction through cold rolling at room temperature, followed by heat treatment at temperatures ranging from 400 to 650 ℃. A comprehensive investigation was conducted into how cold rolling deformation and the aging process affect the alloy's microstructure, as well as its mechanical and electrical properties. The analysis was performed using a scanning electron microscope equipped with a backscattered electron diffraction system (SEM-EBSD), complemented by transmission electron microscopy (TEM). The findings revealed that recrystallization and precipitation occurred concurrently and were both enhanced by higher temperatures and prolonged heat treatment durations. However, recrystallization at elevated temperatures has a marginal impact on enhancing electrical conductivity and results in a significant reduction of mechanical properties. In contrast, alloys preserving the deformed microstructure benefit from multiple strengthening mechanisms, including precipitation, dislocation, grain boundary, and texture strengthening. This study offers quantitative insights into the precipitation and recrystallization behaviors of Cu-Ni-Si alloys, contributing significantly to a deeper understanding of the mass production of high-performance copper alloys.