Research on Grain Coarsening Mechanism of Forged 6061 Aluminum Alloy

Abstract

The mechanism of grain coarsening on the surface of forged aluminum alloy wheels was studied in this work. The as-cast 6061 Al alloy was compressed using a Gleeble−3800 thermal simulation testing machine at 400, 440 and 480 °C with strain rate of 1 s⁻¹, and the true strain value is ~ 0.9. Meanwhile, the effect of deformation temperature on microstructure was analyzed. The evolution of microstructure of the as-compressed Al alloys after solid solution treatment was also clarified. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) were used to characterize the microstructural evolution in details. The results show that the influence of deformation temperature on the microstructure is relatively small. It was found that the average grain size of the Al alloy compressed at 400 °C increased from 53 to 70.2 μm after subsequently solid solution treatment. However, the average grain size of the Al alloys compressed at 440 and 480 °C did not change significantly after solid solution treatment. Moreover, the texture of Al alloy compressed at 400 °C changed from CD (Compression direction)//(110) <101> to CD//(100) <001> after solid solution treatment due to the occurrence of static recrystallization and the growth of specific oriented grains, while the texture type of Al alloys compressed at 440 and 480 °C are remained CD//(110) < 101> after solid solution treatment. Therefore, increasing the deformation temperature can effectively suppress the grain coarsening of forged aluminum alloy wheels.