| As the lightest metal structural material at present,magnesium（Mg）alloy has significant lightweight advantages in infrastructure construction and key fields of national economy and national security.However,the mechanical properties of Mg alloys at room temperature are poor,which reduces the competitiveness of Mg alloys in industrial applications.Therefore,the research on high-strength and tough Mg alloys is of great scientific significance.For the newly developed Mg alloy,studying its hot deformation behavior and determining the suitable hot processing parameters has certain engineering guiding significance for the subsequent plastic processing and application of the alloy.In this paper,the new Mg-6Zn-1Gd-1Er alloy developed by the research group is used as the research material.This alloy has a significant age-hardening response after aging treatment.Mg-6Zn-1Gd-1Er alloy was subjected to hot compression test(180～380℃and 10-3～10 s-1)after solution and aging treatment to study the hot deformation behavior of pre-aged Mg-6Zn-1Gd-1Er alloy,and to determine the appropriate hot processing parameters.The dynamic recrystallization（DRX）behavior,deformation mechanism and mechanical behavior of Mg-6Zn-1Gd-1Er alloy during hot compression were further analyzed combined with the microstructure study,providing theoretical reference and practical guidance for subsequent plastic processing and industrial application of Mg-Zn-Gd-Er alloy.Based on the hyperbolic sine function,the constitutive equations of the pre-aging Mg-6Zn-1Gd-1Er alloy in the medium-high temperature and low-temperature deformation range were established.The hot processing map of the pre-aging Mg-6Zn-1Gd-1Er alloy was constructed.The suitable hot processing parameters are 330～380℃and 10-3～10-2 s-1,and the instability zone was between 180～230℃and 1～10 s-1.The deformation mechanisms in the regions of high efficiency of power dissipation in the hot processing map are continuous dynamic recrystallization（CDRX）,discontinuous dynamic recrystallization（DDRX）and particle stimulated nucleation（PSN）mechanisms.During the hot compression deformation of Mg-6Zn-1Gd-1Er alloy,the volume fraction and grain size of DRX both increased with the increase of temperature,but showed the opposite trend with the increase of strain rate.DRX grains nucleate and grow through the CDRX,PSN and twin-induced dynamic recrystallization（TDRX）mechanism.Under the same deformation conditions,the pre-aged samples are more conducive to the occurrence of DRX than the solution heat-treated samples.Under the action of pyramidal<c+a>slip,the peak texture components of pre-aged samples split from compression direction to transverse direction,and formed bimodal texture.During the hot compression deformation process of Mg-6Zn-1Gd-1Er alloy at 180℃and 330℃,the flow stress curves of the solution heat-treated and pre-aged samples have crossover phenomenon at strains of 0.37 and 0.43,respectively.At 180℃,when the strain is 0.27 and 0.47,the flow stress of the pre-aged sample is larger and smaller than that of the solution heat-treated sample,respectively.The reason is that the interaction of the W phase with dislocations/twins strengthens the alloy,and DRX softening behavior occurs in the pre-aged sample with the increase of strain.At 330℃,when the strain is 0.33 and 0.53,the flow stress of the pre-aged samples is smaller and larger than that of the solution heat-treated sample,respectively.This is mainly due to the fact that the dynamic precipitation phase of the solution heat-treated sample hinders the movement of dislocations and grain boundaries and increases the deformation resistance.As the strain increases,the dynamic precipitation phase promotes DRX,resulting in a smaller flow stress of the solution heat-treated sample. |
