Effect Of Equal Channel Extrusion On Microstructure And Mechanical Properties Of Al-Mg-Si Alloy

In recent decades,the equal-channel angular pressing technology was recognized as one of the most promising technology which can guarantee materials to sub-micron. The theory was press the polycrystalline sample into a specially designed mold for many times without changing cross section shape and made the homogeneous shear deformation for many times,so that it realized the grain refined obviously. It has achieved significant effect in refining grain size, increased of material strength, hardness and deformation ability, and improved the process parameters of materials.This topic selected 6063 bands of Al-Mg-Si alloy as the research object by equal channel angular extrusion, changed with the extrusion path and the extrusion passes for Al-Mg-Si alloy organization(morphology, size and distribution) through comparative analysis.According to the vary of mechanical properties of aluminum alloy, it summed up the strengthening mechanism of alloy; Finally combined solid solution strengthening effect of alloy, optimized the optimum experimental scheme. The results of the study as follows:(1) After homogenized reatment of cast Al-Mg-Si alloy, the grain was uneven distribution, moreover the boundary of grain was obviously. After four times of ECAP distortion, α-Al matrix as submicron grain, and the second phase β(Mg2Si) were refined and diffusely distributed in the matrix with the skeletal shape.(2) There were differences among microstructure through two different extrusion paths.Being extruded by A route, the size of α-Al and β(Mg2Si) were relatively tiny, formed large Angle grain boundary also relatively late; Meanwhile in Bc route, the grain of axial was stepped up, and the uniformity of organization was preferred. What’s more, it slightly formed more large Angle grain boundaries.(3) Compared with cast alloy, After two different paths extrusion(A and Bc) of Al-Mg-Si alloy, the extrusion pressure, hardness and tensile strength increased significantly,but extends led in ascending and then descending, the elongation of extrude aluminum alloy remained invariability; As a whole being extruded by A routes, extrusion force,hardness and tensile strength were slightly higher than Bc routes, but extensibility slightly lower.(4) With increase of the solid solution temperature of Al-Mg-Si alloy equal channel angular pressing state, uniform and compact equiaxed grains were formed, and the hardness led in ascending and then descending. With the increase of aging temperature, precipitatedfrom the second phase(Mg2Si) number increased gradually, hardness and tensile strength led in ascending and then descending. In the aging of 1 hour, elongation rate reached the maximum, after that the elongation of alloy were starting to fall sharply, tensile strength and elongation of aluminum alloy during aging was slightly higher than non in the aging of 8hours.(5) The optimal solution and aging treatment process for the Al-Mg-Si alloy equal channel angular pressing state was 530 ℃ and 4 hours for solid solution then 175 ℃ and 8hours for aging.