Improvement in the anisotropic mechanical properties and formability of Al–Si–Mg–Cu-based alloy sheets

The anisotropic mechanical properties and formability of Al–Si–Mg–Cu-based alloy sheets were investigated by varying their recrystallized grain sizes. By adding Cr and Mn and controlling the homogenization heat treatment, the recrystallized sheets with average grain sizes of 85, 61, 54, and 26 μm were prepared. As the average grain sizes of the recrystallized sheets decreased from 85 to 26 μm, the yield strength (YS) increased from 69.5 to 86.4 MPa due to grain boundary and particle strengthening. At the same time, the elongation was improved because the reduction in the stress concentration delayed the formation of the large-scale necking. The anisotropy in YS and elongation significantly decreased because a large number of fine grains with various orientations operated similar slip systems in all directions. Furthermore, grain refinement can increase and decrease the plastic strain ratio (r‾) and planar anisotropy (Δr), respectively, due to the formation of random textures. A bending formability map was proposed, which showed the acceptable and non-acceptable bending regions based on the grain size and flanging radius. This study provided valuable insight regarding the effects of refining recrystallized grains on anisotropic mechanical properties and formability.