Evolution of neutral layer and microstructure of AZ31B magnesium alloy sheet during bending

Due to the poor formability of magnesium alloy sheet, evolution of neutral layer and microstructure was investigated by V-bending at 423 K. The results show that the neutral axis shifts dramatically toward the tension region of the specimen during V-bending. This is different from that of the general metals, like aluminum, whose neutral layer shifts to the compression region. This effect is attributed to the tension–compression asymmetry between the outer and inner regions of the specimen during bending. Moreover, the enhancing tension–compression asymmetry induced by the inhomogeneous texture formed throughout the thickness of V-bended sheet is also a key factor in the shift of neutral layer.

► Neutral layer shifts to the tension zone in V-bend which is opposite to that of general metal.
► Some twinning bands appear obviously in the middle region, which is rarely reported.
► k-value is an important parameter which is firstly introduced to evaluate the offset of neutral layer of magnesium alloys in bending.
► Microstructure of magnesium alloy in bending has been detected which was rarely reported before.