Gain boundary character distribution optimization of Cu-16at.%Al alloy by thermomechanical process: Critical role of deformation microstructure

To explore the influence of deformation microstructures on the evolution of gain boundary character distribution (GBCD), various thermo-mechanical processes (TMPs) were carried out on the Cu-16at.%Al alloy. The deformation microstructures of all cold rolled samples and the evolution process of twin related domains (TRDs) during subsequent annealing were revealed by transmission electron microscope (TEM) observations and quasi in situ electron back scatter diffraction (EBSD) observations, respectively. Besides, the influence of GBCD optimization on the mechanical property was also examined by uniaxially tensile tests. The results show that the deformation microstructures including stacking faults (SFs) and deformation twins (DTs) have significant effects on the evolution of TRDs and thus on the GBCD optimization. SFs are beneficial to GBCD optimization, for which the formation of annealing twins (ATs) can be induced by generating stacking accidents in a sequence of closely packed atomic planes at the front end of growing TRD. On the contrary, DTs hinder the growth of TRDs, thus impairing GBCD optimization. The optimal prior strain of TMP for the GBCD optimization of the Cu-16at. %Al alloy is thus suggested to be around the threshold strain for the appearance of DTs. Under the premise for the absence of obvious differences in yield strength and ultimate tensile strength, the tensile ductility of the GBCD optimized Cu-16at.%Al alloy is improved, due to an increased deformation uniformity and a higher resistance of AT boundaries to crack propagation.