Clustering ball spinning (CBS) forming is a novel approach to manufacturing a complex curved surface. In order to explore the forming limit of magnesium alloy in the CBS forming process, the modified GTN model was incorporated into the FE simulation to analyze the damage evolution. The theoretical analyses are conducted to investigate the deformation mechanism and to explore the stress state in the CBS forming process. The numerical results show that the modified GTN model can predict the result more accurately compared with the standard GTN model, and the damage parameters for GTN model are determined by the experiments. Besides, the forming limit of AZ31 magnesium alloy can be improved by CBS forming method. To explore the reason for the increased forming limit, the microstructure of curved surface was tested by electron backscattered scattering detection (EBSD). The results demonstrate that the deformation of magnesium alloy plate by the CBS method is dominated initially by the extension twinning, and non-basal slip systems are activated with the development of forming process.
In this paper, a novel manufacturing strategy named as tube pack-rolling (TPR) was proposed. In the process, Mg-6Al-1Zn-0.3Mn (wt%) (AZ61) bar was packed by stainless-steel tube to be rolled at elevated temperature. In order to compare the advantage of TPR, AZ61 bar was also rolled without stainless-steel tube which is named naked-rolling (NR). The stainless-steel was picked as the pack material because of its high strength and hardness which can completely restrain the deformation of magnesium alloy. Numeral simulations were employed to analyze the strip shape and formability. The optimized parameters of contour control are discussed. Tensile tests at room temperature show that specimen rolled by TPR at 673 K exhibit good comprehensive mechanical properties, and the yield strength and ultimate tensile strength reached 213 MPa and 305 MPa with the elongation of 23.2%. The microstructure was investigated by optical microscopes (OM) and electron back scattered diffraction (EBSD). The AZ61 alloy strip rolled by TPR at 673 K exhibited homogenous almost fine dynamically recrystallized equiaxed grains (about 5 µm) with a weak texture. Meanwhile the microstructure evolution mechanism also shows the temperature has significant effect on TPR processing.
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