Study On The Mechanical Behavior And Plastic Deformation Mechanism Of Copper-zinc Alloy Subjected To Short-time Surface Mechanical Grindin

Cu alloy materials are widely used in the electronics industry,electrical industry,transport industry and light industry due to their excellent electrical conductivity,thermal conductivity,ductility and ease of processing,etc.However,the strength of traditional copper alloy materials is relatively low,which severely limits their further development.Numerous researchers have investigated this problem,and in recent years the emergence of heterogeneous structural materials has provided a new direction for research on this issue.The inverse relationship between strength and shape is prevalent in traditional metallic materials,but heterogeneous structural materials are better able to achieve high strength while maintaining good plasticity,which improves this inverse relationship to a certain extent.In this research project,two copper-zinc alloys with different stacking fault energy were chosen:Cu-10wt%Zn(SFE:35 mJ/m2)and Cu-20wt%Zn(SFE:18 mJ/m2).The surface mechanical attrition treatment(SMAT)was carried out on two copper-zinc alloys with different stacking fault energy under liquid nitrogen,and the plastic deformation behavior of the copper-zinc alloys was investigated using Digital Image Correlation(DIC),XRD,EBSD and TEM.Metallographic and hardness tests on the SMAT-treated copper-zinc alloy showed a refinement of the surface grains and a gradual decrease in hardness values from the surface to the core,which remained stable up to a certain depth.The SMAT treatment time of lmin sample had uneven hardness distribution in the depth range of 0-150μm from the surface,with hard and soft zones;while the 2min sample had uniform hardness distribution.The quasi-static tensile test showed that the 20Zn-lmin sample had good comprehensive mechanical properties,with a two times increase in yield strength compared to the annealed sample,uniform elongation of 39%was also achieved.The DIC technique was used to analyze the strain evolution on the surface of the samples and found that strain concentrations appeared earlier after SMAT treatment.In addition,the effects of HDI stress and geometric necessary dislocations on the plastic deformation of the samples during the tensile process were observed by Bauschinger effect and electron backscatter diffraction,and the synergistic strengthening behavior of the heterogeneous structured Cu-Zn alloy material during the deformation process was discovered.XRD technique was also used to measure the dislocation density changes in the tensile process of different stacking fault energy material samples after SMAT treatment,and it was found that the dislocation density of the lower stacking fault energy samples was higher at 10%strain after SMAT treatment.The presence of dislocations,stacking fault and twins in the lower stacking fault energy samples observed by TEM testing,while only dislocations are present in the higher stacking fault energy samples;The mechanism of plastic deformation changed from dislocation slip to stacking fault and twinning as the dominant mechanism.