The Effect of Grain Size on the Bend Forming Limits in AZ31 Mg Alloy

The present study examines the bending behavior of coarse and fine-grained AZ31 magnesium alloy. The corresponding deformation mechanisms are ascertained via tensile, compression, and bending tests in combination with digital image correlation and electron backscatter diffraction. It is shown that grain refinement from 60 mu m to 3 mu m significantly improves tensile ductility, while forming limits in compression and bending show no obvious effect of grain size. Analysis of the microstructure revealed a high density of twin bands in the compression zones of the bent samples. Interestingly, the fine-grained material experienced failure in the compression zone. The fracture strain in bending appears limited by the material ductility in both tension and compression. The outcome of this study is that in magnesium alloys grain refinement may not always be an effective method for the improvement of ductility, particularly when bending of the type considered here is dominant.