Effect of Mg addition on Fe phase morphology, distribution and aging kinetics of Cu-6.5Fe alloy

Abstract

The microstructure and properties of the Cu-6.5Fe- x Mg ( x = 0, 0.1, 0.3, 0.5 wt%) alloy were investigated by TEM (transmission electron microscopy), EBSD (electron backscattered diffraction) and tensile testing machines to explore the effect of Mg addition on Fe phase morphology, aging kinetics and properties of Cu-6.5Fe alloy. The properties testing discovered that the addition of Mg significantly improved the tensile strength of Cu-6.5Fe alloy but slightly reduced its conductivity. The tensile strength and conductivity of Cu-6.5Fe-0.3 Mg alloy were 704 MPa and 60.2 %IACS, respectively, after aging 300 °C for 1 h. Compared with Cu-6.5Fe alloy, the tensile strength of Cu-6.5Fe-0.3 Mg alloy increased by approximately 236 MPa, and the conductivity decreased by only 1.9 %IACS. The microstructure observation showed that the addition of Mg significantly refined the Fe phase and inhibited its dendrite segregation. After large strain plastic deformation, the granular Fe phases transformed into Fe fibers and the Fe fibers distributed denser with the addition of Mg. Furthermore, the addition of Mg promoted the precipitation of the Fe phase and effectively inhibited the recrystallization of the Cu matrix during the aging. The recrystallization of Fe phase and coarsening of the precipitated Fe phase were also inhibited. The evolution mechanism of Fe phase during casting, plastic deformation and aging in Cu-6.5Fe-0.3 Mg alloy is proposed. • Mg reduces the solid solubility of Fe in Cu and inhibits the segregation of Fe. • Fe phase distribution in Cu–Fe–Mg alloy is more uniform. • Mg reduces Fe fiber spacing and increases Fe fiber density. • Mg inhibits the recrystallization of the Cu matrix and Fe phase and refines the recrystallized grains. • Mg significantly improves the tensile strength of Cu–Fe alloy and has little effect on electrical conductivity.