Microstructure and properties of Cu–Cr–Mg and Cu–Cr–Mg–Si alloys treated by multi-stage thermo-mechanical treatment

Abstract

Cu-0.45Cr-0.15 Mg and Cu-0.45Cr-0.15Mg-0.02Si (wt.%) alloys exhibit excellent comprehensive properties after treated by multi-stage thermo-mechanical treatment, achieving the combination of high strengths and high conductivity, with hardness of 171 HV and 179 HV, electrical conductivity of 78.8 %IACS and 79.9 %IACS, tensile strengths of 555 MPa and 600 MPa and elongation of 5.6% and 6.7%, respectively. There were three forms of precipitation observed in the different stages of aging: coffee-beans, Moiré fringes, and rod-like precipitates, and more precipitation in Cu-0.45Cr-0.15Mg-0.02Si alloy, which illustrates the addition of Si promotes the precipitation of Cr and refines precipitation, preserving high density of dislocation, achieving superior strength and conductivity. The calculation of strength and conductivity indicates that precipitation and dislocations play a significant role in the increase of yield strength and dissolved atoms are the main source of resistance.