Age hardening behaviors of spun 2219 aluminum alloy component

The role of spinning in the age hardening behaviors of 2219 aluminum alloy and the underlying mechanisms are very vital for aging process design. To this end, the Vickers hardness (HV) and microstructure features of spun 2219 Al-alloy component under various spinning thicknesses are investigated. The results show that the aging hardness curve under low thickness reduction is characteristic of dual-peak at artificial aging time of 2 h and 18 h, respectively, while the second peak diminishes with reduction and disappears as the reduction is larger than 10%. Furthermore, the hardness of the component decreases with the increase of the reduction after aging for 18 h, showing a completely contrary tendency compared with the hardness variation at the first aging hardness peak. The rapid precipitating of the fine second phases at the beginning of aging period leads to the sharp rise in hardness and thus the formation of the first hardness peak at 2 h aging time. For the spun component with reduction smaller than 10%, the formation of the second aging hardness peak is resulted from the transformation of θ” phase to θ' phase. When the thickness reduction is larger than 10%, a large number of dislocation cells and sub-grain boundaries are produced by the shear spinning deformation. These dislocation cells and sub-grain boundaries lead to the formation of the coarse and non-uniformly distributed precipitates in aging process, which causes the monotonous decrease in hardness after aging for more than 2 h.