粗晶Mg-3Gd-1Zn合金高温压缩变形过程中的动态再结晶

研究了粗晶Mg-3Gd-1Zn合金在723 ～823 K,应变速率0.100 ～0.001s-1条件下单轴压缩变形过程中的动态再结晶行为.研究结果表明,其热压缩曲线为典型的动态再结晶型,峰值流变应力和稳态流变应力随温度的升高而减小,随应变速率的增大而增大；在该实验温度范围内其变形激活能约为140 kJ·mol-1；再结晶晶粒尺寸lnd与lnZ参数偏离线性关系,且变形温度对再结晶晶粒尺寸的影响比应变速率更大.利用金相和电子背散射技术(EBSD)对773 K,0.010 s-1条件下压缩不同变形量的Mg-3Gd-1Zn合金进行了组织表征,发现其动态再结晶大都发生在孪晶界及其与原始晶界的交叉处,主要为孪生诱发动态再结晶形核(TDRX)机制.再结晶形核初期形状不规则,晶界倾向于呈直角,随着应变量的增大,由于晶界的局部迁移,再结晶晶粒逐渐转变为稳定的等轴晶.

Dynamic Recrystallization of Coarse-Grained Mg-3Gd-1Zn Alloy during Hot-Compression

The dynamic recrystallization behavior in coarse-grained Mg-3Gd-1Zn alloy during uniaxial hot-compression of temperature 723～823 K and strain rate 0.100～0.001 s-1 was investigated.The result indicated that the hot-compression curves were typically dynamic recrystallization characteristic,the peak slow stress and steady slow stress decreased when the deformation temperature increased and strain rate decreased;the deformation active energy was about 140 kJ · mol-1 within the temperature range;the conventional relationship between DRXed grain size and the Z parameter broke down.Compared with the strain rate,the deformation temperature had more significant influence on the DRXed grain size.The microstructure evolvement of Mg-3Gd-1Zn alloy deformed at 773 K,0.010 s-1was investigated with metallography and EBSD technique.The results showed that DRX occurred mainly at the primary tensile twins and its intersection with the original grains and the DRX mechanism was mainly the "Twin" DRX.The new grains formed in twins were in non-equilibrium states and exhibited almost rectangular shape,and they gradually transformed to stable equiaxed grains in high strain owing to the local boundaries migration.