Experimental study on axial closed die rolling thermo-mechanical treatment of 6061 aluminum alloy

The microstructure and mechanical properties of 6061 aluminum alloy were studied by using the aging treatment of 540 ℃/3 h solid solution+60% reduction axial closed die rolling+180 ℃/1.5-8 h. Comparison was made with the aging treatment of 60% reduction rolling+540 ℃/3 h solid solution+180 ℃/8 h. The results show that after axial closed die rolling thermo-mechanical treatment, the dislocation density of the aluminum alloy increases, the PFZ width decreases, and the spheroidized β″ phase appears. The aluminum alloy obtains good comprehensive mechanical properties at the aging time of 2.5 h, the yield strength of 333 MPa and the tensile strength of 359 MPa. As the aging time gets longer, little change took place in the grain size of the aluminum alloy, the granular Mg 2 Si precipitates in the grain decrease, and a small amount of coarse granular Mg 2 Si precipitates appear at the grain boundary. The dimple at the tensile fracture gradually changes from large and deep to small and shallow, and the ductility of the aluminum alloy decreases with the aging time.