Gd对冷旋锻制备纳米晶镁合金的影响

Effect of Gd on preparation of nanocrystalline Mg alloys via cold rotary swaging

通过显微硬度测试、拉伸试验和透射电镜手段研究Gd元素对冷旋锻过程镁合金纳米化的影响。结果表明,由于纯镁中很难形成位错阵列,旋锻不能实现纯镁纳米化。相比之下,单独添加Gd,旋锻后镁合金晶粒可得到显著细化。在旋锻早期阶段,纯镁和Mg−Gd合金中都形成孪晶片层。随着增加旋锻变形的继续,相比纯镁,更多的非基面位错在Mg−Gd合金中形成,这促进了Mg−Gd合金中位错阵列的形成,导致合金纳米化。随着Gd含量的增加,Mg−Gd合金晶粒细化效果显著提升,晶粒细化至100 nm以下的临界Gd含量约为5.4%(质量分数)。

The effects of Gd element on the nanocrystallization of Mg alloys during swaging were studied by means of the microhardness test,tensile test,and transmission electron microscopy.The results indicate that it is impossible to achieve nanocrystallization in pure Mg via rotary swaging,which may be attributed to the difficulty of forming dislocation arrays.In contrast,adding Gd alone can achieve a remarkable grain refinement effect after swaging.In the early stage of swaging,twin lamellae are all formed in the pure Mg and Mg−Gd alloys.As the swaging process continues,more non-basal dislocations are formed in the Mg−Gd alloys than in pure Mg.This promotes the formation of dislocation arrays and the resulting nanocrystallization in the Mg−Gd alloys.As the Gd content increases,the refinement effect is obviously enhanced.The critical content for the refinement of the grain size below 100 nm is about 5.4 wt.%.