Study On Microstructure And Mechanical Properties Of Mg-6Al-1.0Ca-0.5Mn-xSn Alloys

In this paper, as-cast Mg-6Al-1.0Ca-0.5Mn-xSn(x=0,1,3,6)(T1, T2, T3,T4) alloys were the research objects, which were processed by plastic deformation(extrusion, rolling) and heat treatment process(solid solution and aging). The influence of Sn elements, plastic deformation and aging time on microstructure and mechanical properties were studied.The conclusions have obtained from the experiment:(1) The dendritic spacing decreases with increasing Sn element content,while the amount of Mg2 Sn phase precipitation increases gradually and the irregular shape of ?-Mg17Al12 phase becomes blocky. Mg-6Al-1.0Ca-0.5Mn-6Sn alloy has minimum dendritic spacing and the best comprehensive mechanical property. Its tensile strength, yield strength, hardness and elongation were 190.4MPa, 117.7 MPa, 57.8 HB, 9.31%, respectively.(2) The dynamic recrystallization occurred, the alloy grain is refined dramaticlly, and ?-Mg17Al12 phase and Mg2 Sn phase mainly distributed in grain boundary by granula, during the extrusion process of the solid-soluted Mg-6Al-1.0Ca-0.5Mn-xSn(x=0,1,3,6). The grain of extruded Mg-6Al-1.0Ca-0.5Mn-6Sn alloy was the finest, and its average grain size of 8.88 ?m. After aging treatment, the grain size of extruded alloys increased slightly. The fine second phase particles precipitated dispersedly with the increase of Sn content.(3) After extrusion deformation, the strength and elongation of Mg-6Al-1.0Ca-0.5Mn-xSn(x=0,1,3,6) alloys increased significantly. The strength of Mg-6Al-1.0Ca-0.5Mn-6Sn alloy was the largest, and its UTS, YS,hardness and elongation of 306.3 MPa, 220.7 MPa, 62.8 HB, 15.31%,respectively. After aging treatment, the hardness change trend of four extruded test alloys was initially increases and then they are stable with the increase of aging time, and its aging time of peak hardness of 48 hours. As the Sn content increased, the strength and hardness of the test alloys after the peak aging treatment increased, but the elongation decreased. The strength of extruded testalloy increased, because of alloy fine crystal strengthening and precipitation strengthening.(4) After rolling deformation, its strength and hardness increased while the elongation decreased. The cold-rolled Mg-6Al-Ca-0.5Mn-6Sn alloy has the highest strength, and its UTS, YS, hardness and elongation of 351.3 MPa, 262.4MPa, 65.2 HB, 7.92%, respectively. After the aging treatment of 30 hours, rolled test alloy got peak hardness, and its strength were further improved. The strength of the cold-rolled alloys is always higher than that of hot-rolled alloys.