Study on hot deformation behaviuor of Mg-7.1Gd-2.8Y-1.3Nd-0.4Zn magnesium alloy using hyperbolic sine equation and processing maps

Addition of rare earth (RE) elements to magnesium alloys has developed the Mg-RE alloys having high specific strength to be used in the aerosapace and automobile industries. Deformability of Mg alloys is limited due to hexcagonal closed packed (HCP) structure and the alloys are routinely processed by hot deformation. The aim of this study is investigation of hot deformation behavior and developed a con-stitutive model for Mg-7.1Gd-2.8Y-1.3Nd-0.4Zn (wt%) alloy. Therefore, hot compression tests were performed at temperature interval of 400ºC-475ºC and at strain rates in the range of 0.001s-1-1s-1 with maxiumum strain of 0.6 on as-extruded specimens. The hyperbolic-sine analysis showed that the stress power (n) and the activation energy (Q) of the investigated alloy are 4.92 and 307.42 kJ.mol-1, respectively. The processing maps were drawn based on the dynamic material model (DMM) in the study of the alloy. The maps suggest two stable domains at: (1) 475ºC-0.001s-1 and (2) 425ºC-460ºC at the strain rates of 0.005s-1-0.05s-1, and indicate a wide unstable region below 425ºC.