During hot deformation, continuous dynamic recrystallisation (CDRX) is believed to occur, and even dominates microstructural evolution in many metallic materials with high stacking fault energy, such as aluminium alloys. A unique material model for hot deformation of aluminium alloys is proposed in this paper, based on consideration of two processes: (i) increase of dislocation density, induced by plastic deformation, leading to generation, rotation and migration of low angle grain boundaries (LABs) and their transformation into high angle grain boundaries (HABs); (ii) migration of HABs leading to annihilation of both LABs and HABs. At large strain, the above counteracting processes, guided by different mechanisms, lead to saturation of HABs fraction. The model is applied to hot deformation of AA5052 and AA7050 alloys under various temperatures and strain rates, and calculated flow stress, HABs fraction and grain size evolution for both alloys agree well with the corresponding experimental data. The capability of predicting saturation of HABs fraction and average subgrain misorientation angle of both alloys under large strains demonstrate the potential applicability of the model to a wide range of hot forming process conditions.
Aluminum alloy 7075 is one of the materials widely used in the manufacture of structural components used by aviation industries. High precision is required in producing the shapes of such components due to shape stability and dimensional accuracy being difficult to maintain throughout the different stages of manufacturing. In this work, an experimental study of the effect of VSR (Vibratory Stress Relief) on the deformation and residual stresses of aluminum alloy 7075 thin-walled components is presented. It was concluded that VSR improved the shape and size stability of the material to a significant level by relieving induced residual stresses in the thin-walled parts. Finally, more uniform residual stress distribution was obtained after the VSR treatment, compared to before the VSR treatment. This proved that VSR has a significant influence on improving the shape stability of the thin-walled aluminum alloy 7075 components.
Relieving the residual stress in components is essential to improve their service performance. In this study, a roll-bending process was proposed to reduce the quenching residual stress in a large-size 2219 Al alloy ring. The roll-bending effect on quenching residual stress was evaluated via the finite element method (FEM) combined with experiment. The effect of radial feed quantity, friction coefficient, and roller rotational speed during the roll-bending process on quenching residual stress was analyzed. A set of optimized roll-bending parameters with radial feed quantity, friction coefficient, and roller rotational speed was obtained. The results reveal that the best reduction rates of circumferential and axial residual stress reached 61.72% and 86.24%, respectively. Furthermore, the difference of the residual stress reduction effect between the roll-bended ring and the three-roller bended beam was analyzed.
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