Microstructural stability and mechanical response of Cu–Ag microcomposite wires

Abstract

A transmission electron microscope (TEM) was used to study the microstructural and mechanical stability of Cu–24 wt% Ag microcomposites in both the as-drawn and heat-treated condition. Three phase morphologies were observed in the heavily drawn Cu–24 wt% Ag wires: fine silver filaments, thick silver lamellae, and copper-rich α phase. The microstructure of the Cu–Ag microcomposite was observed on a much finer scale than that reported by previous investigators. The stress–strain responses and fracture behavior of Cu–Ag microcomposite wires were also examined and correlated with the microstructural change caused by thermomechanical treatments. The ratios of yield stresses (0.86) and ultimate tensile strengths (0.83) at 295 and 77 K were quite close to the ratio of Young's moduli (0.85), suggesting that the strengthening mechanism is predominantly controlled by long-range athermal obstacles. A modified rule of mixtures was used to predict the strength of the Cu–24 wt% Ag microcomposites. The strength of each of the three regions observed by TEM was evaluated or estimated based on the available data. The predictions of the model were in good agreement with experimental data.