Flow behavior and formability of hot-rolled Mg-8Gd-3Y alloy under double-pass isothermal compression

Multi-pass hot rolling can help overcome the poor formability of high-strength Mg-Gd-Y alloys at ambient and intermedium temperature. It is essential to explore deformation characteristics of the alloys under such discontinuous thermomechanical processing. In the current work, double-pass isothermal compression tests were carried out to study the flow behavior and formability of a hot-rolled Mg-8Gd-3Y alloy at the temperature range of 350-450 degrees C with a strain rate range of 0.001-0.1 s(-1). Two kinds of hardening behavior characterized by higher second-pass peak stress than the first-pass unloading stress are discovered. One is caused by precipitation that occurs during holding at a temperature range of 350-400 degrees C under a strain rate of 0.1 s(-1). The other is grain-growth-induced hardening and takes place at 450 degrees C with a strain rate range of 0.01-0.1 s(-1). Based on the dynamic material model, three-dimensional power dissipation and instability maps were established, corroborating improved formability under double-pass isothermal compression. The results clarify that employing inter-pass holding during hot working can widen the suitable processing window and reduce deformation bands.