模具结构对反复模压变形5052铝合金显微组织的影响

Influence of die construction on microstructure of 5052 aluminium alloy processed by repetitive groove pressing

在自制的新型组合式模具上对商业5052铝合金板材进行两种不同结构模具下的反复模压变形,并用光学显微镜和透射电镜对变形合金进行显微组织分析。结果表明:限制模压(Constrained Groove Pressing,CGP)变形和非限制模压(UnconstrainedGroove Pressing,UGP)变形均能够有效细化5052铝合金,其平均晶粒尺寸随变形道次的增加而减小。在两种不同结构模具的反复模压变形下,5052铝合金呈现出不同的组织特征。经CGP变形后合金组织基本由破碎的等轴小晶粒构成,形成包含高密度位错的等轴状亚晶;而经UGP变形后,形成类似于冷轧变形金属组织的拉长晶粒和具有较大取向差的包含高密度位错的带状亚结构。与UGP相比,CGP更有利于晶粒细化和形成等轴晶粒。

Microstructure of commercial 5052 aluminum alloy subjected to repetitive groove pressing,using a novel self-designed groove pressing die,was investigated by optical microscopy and transmission electron microscopy.The results show that grain refinement has been achieved using constrained groove pressing（CGP） or unconstrained groove pressing（UGP）.The average grain size gets decreased with the increasing of the number of pressing.But the microstructure of the samples processed by different groove pressing methods exhibits different characteristics.The samples processed by CGP exhibit equiaxed ultra-fine grains and subgrains with high dislocation density inside.The microstructure of the samples subjected to UGP can be characterized as elongated grains and a uniform distribution of dense dislocation microbands which have misorientation from one region to another.Compared with UGP,CGP is more beneficial to grain refinement and formation of equiaxed grains.