The effect of induced precipitations and pre-twins on the bending neutral layer migration behaviors of AZ80 Mg alloy sheet

To explore the effect of the precipitated phase particles and twins on the microstructure evolution and neutral layer evolution during bending, {10–12} tensile twins were introduced along the transverse direction (TD) on AZ80 Mg alloy sheets at room temperature. Then pre-compressed samples were aged to induce more precipitations. The reverse tensile tests were carried out at room temperature, and the three-point bending deformation was carried out at 100 °C. After aging treatment, precipitations increased. The results showed that twin crystals can promote precipitation formation. And the YS (yield strength) values of the pre-twinned aged samples were significantly larger than that before aging. During the bending process on the pre-compressed samples, the outside of the sample was dominated by the detwinning behaviors, while the inside region was dominated mainly by twinning. For pre-compressed bending samples, the k values were smaller than the initial bending sample. The tension and compression asymmetry in its inner and outer regions was weaker than that of the original bending sample. The existence of precipitations hindered the detwinning behaviors in outside the pre-twinning aged bending samples, and the twinning in inner region was restrained as well so that the inner and outer tension asymmetry decreased. The k values were smaller than that of the unaged samples, which was beneficial to weaken the bending springback of Mg alloy sheets.