A unique spinning method for grain refinement: repetitive shear spinning

摘要

Grain refinement is an effective way to improve the strength of non-heat treatment aluminium alloy. To obtain much refined grains in the spun parts made of 3003 aluminium alloy, a unique spinning method, i.e., repetitive shear spinning, is proposed. The new process is composed of two shear spinning passes conducted along the two sides of sheet metal sequentially. By using finite element (FE) simulation and physical experiment, the grain refinement in the repetitive shear spinning is investigated. The results indicate that, under the same thickness reduction ratio, both the larger equivalent plastic strain and the larger shear strain can be obtained in the repetitive shear spinning than those obtained in the traditional single-pass and two-pass shear spinning processes. Meanwhile, the density of plastic dissipation energy (DPDE) in the repetitive shear spinning process is larger than that in two- pass shear spinning and doubled compared with that in single-pass shear spinning. This makes more deformation energy to be transformed into the stored energy thus provides more driving force for grain refinement. The observation of microstructure indicates that after the repetitive shear spinning, a great number of refined grains are generated with the average grain size refined from 48.6μm of the initial microstructure to 3.77μm, which is smaller than the grain size of 7.17μm and 4.91μm in single-pass and two-pass shear spinning, respectively. With the grain refinement, the micro hardness and its homogeneity of spun part after repetitive shear spinning is improved obviously. Compared with the average standard deviation of micro hardness obtained by the single-pass and two-pass shear spinning, it is decreased by 70.27% and 61.41% under the same thickness reduction ratio. The developed repetitive shear spinning process thus has the good capability for grain refinement and enhancement of mechanical properties of the spun parts and the promising application potential in industries.