Effect Of Si Addition And Deformation Temperature On Microstructures, Mechanical Properties And Annealing Behaviors Of Cu-20Zn Alloy

:With the development of manufacture, more and more metal components are required to be of both high strength and high ductility. Commonly, the sub-micron and nanometer materials prepared by severe plastic deformation (SPD) have high strength, but inferior ductility and thermostability which restrict their wide application in industry. Therefore, it is worth studying on how to promote the strength of alloys without deteriorating their ductility and thermostability. In this research, the effect of Si addition and deformation temperature on microstructure, mechanical properties and annealing behaviors of Cu-20Zn alloy were investigated by optical microscope (OM), transmission electron microscope (TEM), X-ray diffraction (XRD), tensile text and microhardness measurement. Cu-20Zn alloy with high strength and ductility was obtained through the adjustment of rolling condition and annealing treatment.Dislocation density and twin density in Cu-20Zn alloy generated in cold rolling increased with the increasing of Si addition after cold rolling, leading to the enhancing in both strength and ductility. Comparing with Cu-20Zn alloy, the tensile strength of Cu-20Zn-1.9Si alloy raised52%percent and reach to1002MPa. According to XRD and TEM results, it has been proved deformation twins play an important role in enhancing strength of Cu-20Zn-Si alloys apart from dislocation-dislocations and solution strengthening.As the silicon concentration increased in Cu-20Zn alloy, the recrystallization temperature improved from300℃to340℃and grain growth were hindered during annealing. The grain growth had little influence on microhardness when annealed at the temperature between340℃and380℃. Moreover, the k value increases with the decreasing of SFE by adding silicon into Cu-20Zn alloy, resulting in more strengthening in Cu-20Zn-Si alloys, hence, Cu-20Zn-Si alloys obtained a higher strength and better ductility than that of Cu-20Zn alloy. Cryorolling encouraged more twinning and dislocation accumulation when comparing with cold rolling, leading to the distinct enhancement of microhardness and tensile strength. Therefore, cryorolling provided more stored energy for the Cu-20Zn and Cu-20Zn-1.2Si alloy, which would enable more nucleation sites to be formed during subsequent SRX, than the cold rolling do. Furthermore, the activated energy for recrystallization of cryorolled Cu-20Zn-1.2Si alloys is184kJ/mol, which is lower than that of cold rolled ones (217kJ/mol).Additionally, cryorolled Cu-20Zn alloy or Cu-20Zn-1.2Si alloy obtained a superior combination of strength and ductility than that of the cold rolled one after annealing treatment, owing to the finer grain and more nanoscale twins generated by cryorolling. And the ductility of Cu-20Zn-1.2Si alloy was mainly controlled by recrystallization fraction during annealing. A tensile strength of787MPa and an elongation to failure of14.3%were obtained for the Cu-20Zn-1.2Si alloy after cryorolling and annealing at280℃for5hours.