Effect of stacking fault energy on the restoration mechanisms and mechanical properties of friction stir welded copper alloys

Abstract

Pure copper and Cu-Zn plates were friction stir welded under the same condition to evaluate the effect of stacking fault energy on the microstructural evolution and mechanical properties of the joints. For this aim, microstructure and texture of the joints were systematically characterized by electron backscattered diffraction and transmission electron microscopy. Moreover, to study the mechanical properties of the different microstructural zones of the joints, nanoindentation tests were employed. The results showed that in pure copper, continuous dynamic recrystallization was the only restoration mechanism for the formation of new grains. By adding zinc into copper, namely decreasing stacking fault energy, both continuous and discontinuous dynamic recrystallization mechanisms occurred. To this end, the effect of stacking fault energy on the restoration mechanisms has been summarized by schematic models. Moreover, the effect of the restoration mechanisms on the yield strength and strain hardening behavior of the joints has been scrutinized. Keywords: Friction stir welding, Stacking fault energy, Dynamic recrystallization, Electron backscattered diffraction (EBSD), Transmission electron microscopy (TEM)