Effect of ball milling time and heat treatment on microstructure and properties of 6061 aluminum alloy

The 6061 aluminum alloy was prepared by powder metallurgy method, and the effects of ball milling time and solution-aging treatment on microstructure and mechanical properties of the extruded alloy were studied by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, hardness test and tensile test, etc. The results show that with the prolongation of the ball milling time, the powder morphology gradually changes from spherical to flat sheet, and the powder particle size gradually increases. The sintered alloy has better density and comprehensive mechanical properties when milling for 2 h, but longer milling time will lead to the decrease of density and mechanical properties of the material. The better solution-aging process of sintered alloy after hot extrusion is 530 C-degrees x 1 h+180 C-degrees x 8 h, at which time the alloy precipitates a diffuse distribution and a fine beta" phase, and the alloy has high strength (442 MPa) and hardness (125HV), as well as suitable elongation. Its excellent mechanical properties are mainly the result of the combination of dispersion strengthening, fine grain strengthening and solid solution strengthening.