镁合金中位错滑移和形变孪生的交互作用

镁合金中位错滑移和形变孪生的交互作用

苏虎虎¹，周信哲¹，杨志卿^1*，叶恒强²

（1.中国科学院金属研究所 沈阳材料科学国家研究中心，辽宁 沈阳110016；2.季华实验室，广东 佛山528251）

摘 要  利用像差校正扫描透射电子显微术和界面缺陷理论研究了Mg-9.0Gd-3.0Y（wt.%）合金在多向锻造过程中产生的位错滑移、孪生变形以及位错与孪晶界的反应。不论是孤立的基面〈a₆₀〉位错，还是小角晶界处的基面〈a₆₀〉位错，往往具有紧密的位错芯；锥面〈c+a₆₀〉和〈c+a_s〉位错在基面上分解为扩展位错。溶质原子Gd/Y在合金多向锻造过程中周期性地偏聚在 、 和 孪晶界上。基面滑移和 形变孪生是合金的主要塑性变形模式。位错与 孪晶界的反应可在孪晶界上产生含有残余位错的台阶或凸起，同时释放若干孪生位错，造成孪晶界迁移。实验结果有助于理解在镁合金塑性变形过程中孪晶界原子构型演变、迁移能力以及其对合金塑性变形的影响。

关键词 镁合金；位错滑移；孪生变形；变形机制；像差校正电子显微学

中图分类号：O71；O77；TG111.2；TG115.21⁺5.3；TG146.2⁺2 

文献标识码：Adoi:10.3969/j.issn.1000-6281.2020.06.007

Interactions between slip dislocations and twin boundaries in a Mg alloy

SU Hu-hu¹, ZHOU Xin-ze¹, YANG Zhi-qing^1*, YE Heng-qiang²

(1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang Liaoning 110016；2. Jihua Laboratory, Foshan Guangdong 528251, China)

Abstract   Dislocation slip, deformation twining and their reactions in a Mg-9.0Gd-3.0Y (wt. %) ally processed by multidirectional impact forging were investigated using atomic-resolution aberration-corrected scanning transmission electron microscopy and the interfacial defect theory. The core of most basal 〈a₆₀〉dislocations shows a compact structure, while pyramidal 〈c+a_s〉and 〈c+a₆₀〉dislocations are decomposed into  Frank partial dislocations. Solutes Gd/Y segregated periodically at ,  and  twin boundaries in the samples during multidirectional impact forging. Basal slip and  deformation twinning are the main plastic deformation modes in this Mg-9.0Gd-3.0Y alloy. Reactions of slip dislocations with  TBs could produce steps or facets with residual dislocations and multiple twinning dislocations which could glide along TBs, resulting in their migration. Our atomic-resolution results provide insights into the structure evolution and migration of TBs upon reactions with dislocations, and their influence on plastic deformation of this Mg alloy.

Keywords   magnesium alloys；dislocation；deformation twinning；deformation mechanism；aberration-corrected electron microscopy

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