应变速率对Mg-13Gd-4Y-2Zn-0.5Zr镁合金旋转反挤压的影响

Effect of Strain Rates on Rotary Backward Extrusion of Mg-13Gd-4Y-2Zn-0. 5Zr Magnesium Alloy

旋转反挤压是一种将旋转运动和正常反挤压运动相结合的塑性成形新方法,可以实现Mg-13Gd-4Y-2Zn-0. 5Zr镁合金的剧烈塑性变形,改善其组织和性能。以旋转挤压为工艺对象,利用Gleeble-3500热模拟机研究了镁合金杯形件成形过程中应变速率对材料组织和性能的影响规律。结果表明:Mg-13Gd-4Y-2Zn-0. 5Zr镁合金杯形件旋转反挤压过程中,显微硬度分布较为均匀,试样从外部到内部的晶粒逐渐细化,沿旋转方向动态再结晶程度逐渐提高,晶粒尺寸逐渐减小。在周向应变速率ε周从0增大到0. 05 s^(-1)的过程中,动态再结晶晶粒的占比逐渐上升,在ε周为0. 005 s-1时,片状LPSO相的破碎使此时材料的硬度提高,并抑制了动态再结晶晶粒的产生。ε周的继续增加使位错密度增大,促进了动态再结晶。在旋转反挤压进行过程中,随时间的增加成形载荷波动上升,且随着ε周的增加,成形载荷逐渐下降。

Rotating back extrusion is a new forming method which combines rotational motion with common reverse extrusion.It can realize a severe plastic deformation of Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy and improve its microstructure and properties.Based on rotating back extrusion,the influence of the strain rate on microstructure and properties during the forming process of magnesium alloy cup are studied by using Gleeble-3500 thermal simulator.The results show that in the process of rotating back extrusion of Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy cup,the microhardness distribution of the magnesium alloy becomes more uniform,the grain size inside the sample gets thinner than the outside,the dynamic recrystallization degree increases gradually along the rotation direction and the grain size gradually decreases.As the strain rate increases from 0 s^-1 to 0.05 s^-1,the proportion of dynamic recrystallized grains increases.When the strain rate is 0.05 s^-1,the sheet LPSO phases begin to break up,which makes the hardness of the material increases and inhibits the generation of dynamically recrystallized grain.With the strain rate keeping on raising,the dislocation density increases,which promotes dynamic recrystallization.During the process of rotating backward extrusion,the fluctuation of the forming load increases with time,and the forming load gradually decreases with the raising of strain rate.