Effect of Post-Aging on Microstructure and Mechanical Properties of an Ultrafine-Grained 6061 Aluminum Alloy
Al-Mg-Si alloys are widely used in automotive body panels and parts of the engine owing to their low density,medium strength,high specific strength,good corrosion resistance and other charac-teristics.Currently,there are many studies on the precipitation behavior of undeformed Al-Mg-Si alumi-num alloy,but there is a lack of research on the precipitation evolution and precipitation strengthening mechanism of ultra-fine grained 6061 aluminum alloy at different post-aging temperatures.In this study,the microstructure and mechanical properties of an ultrafine grain 6061 aluminum alloy produced by com-bining the equal channel angular pressing(ECAP)and post aging methods was comparatively evaluated via TEM,XRD,microhardness tests,and tensile tests.The results indicated that the average grain size of the alloy after two ECAP passes was refined to 210 nm.The average grain size of the alloy after the ECAP pass at 80℃ and 20 min post aging was 278 nm;moreover,the fine needle β'',L phase,and Q'phase precipitates at nanoscale were dispersed in the matrix.Furthermore,the tensile and yield strengths were 514 and 483 MPa,respectively,while maintaining a remarkably uniform elongation of 15.1%.These results indicate that numerous dislocations introduced by ECAP in the matrix provide a lo-cation for the nucleation of the precipitate,which accelerates the precipitation kinetics during the post ag-ing process.The high strength and toughness of the ECAP alloy after low temperature post aging can be attributed to the grain refinement strengthening,dislocation strengthening,and nanoprecipitation strength-ening.Thus,the evolution of the aging precipitates during the ECAP and post aging alloy was analyzed.
Al-Mg-Si-Cu alloyultrafine grainlow temperature post-agingmicrostructuremechan-ical property
万方数据
维普
