Effects of precipitation hardening heat treatment conditions on the microstructure, mechanical properties, and electrical conductivity of Cu - 0.4%Cr alloy

In this paper, the effects of the aging temperature on the microstructure, mechanical properties, and electrical conductivity of Cu-0.4% Cr are investigated. The solid solution treatment was performed at 950 ᵒC for 1 hour. Then the samples were aged 5 hours at 200, 300, 400, 500, and 600 ᵒC. The microstructure of the samples was surveyed using FESEM. An analytical model is also developed to predict the age-hardened samples yield stress and the precipitation of the alloying elements based on the microstructure images analysis and electrical conductivity of the samples. Increasing the aging temperature up to 500 ᵒC, the number of precipitates increases and their size decreases. Yield strength, tensile strength, and work hardening exponent at aging temperatures of 200 and 300 ᵒC decreases a little and increases at 400 and 500 ᵒC and then decreases at higher temperatures. In optimum precipitation hardening conditions, the yield strength and tensile strength are higher 51.7 and 21.7% than solid solution treatment, respectively. Electrical conductivity increases by the aging temperature increasing up to 500 ᵒC and then remains almost constant at higher temperatures. Comparison between the tensile test and the present model results shows that the model is capable to predict the yield strength of the age hardened samples by good accuracy.