工程科学学报，第41卷，第7期：898-905,2019年7月 Chinese Journal of Engineering,Vol.41,No.7:898-905,July 2019 D0L:10.13374/j.issn2095-9389.2019.07.008;htp:/journals.usth.edu.cm 经验原子势下铝镁合金中溶质原子向位错芯迁移的最 低能量路径 李晓彤2)，汤笑之)，郭雅芳)四 1)北京交通大学土木建筑工程学院，北京1000442)北京交通大学土木工程国家级实验教学示范中心，北京100044 区通信作者，E-mail:yfguo(@bjt.cdu.cn 摘要铝镁合金在制造业中应用广泛，但其在特定应变率下的塑性失稳不利于加工应用.溶质原子与位错的交互作用是塑 性失稳的微观机理.本文采用势能曲面过渡态搜索技术计算了铝镁合金中替代型溶质镁原子向位错芯迁移的过渡态，确认了 溶质原子与位错芯的交互作用范围，并采用过渡态理论估算了迁移扩散所需的时间，且区分了无空位及有空位参与迁移两种 情况.结果表明，位错压应力区内的溶质原子迁移无明显规律，而在位错拉应力区内，随着溶质原子与位错间距的缩短，迁移 势能垒和系统总能量均逐渐降低.说明目前广泛采用的经验原子势可以很好地反映溶质原子易朝位错拉应力区偏聚这一现 象.溶质原子迁移的过渡态证实迁移过程中的微观结构变化因溶质原子所处位置不同而各异，而交互作用范围不超过约2 m.空位参与对迁移的辅助作用被量化为迁移热激活时间的缩短，并得出其可在微秒量级.当溶质原子完成迁移稳定至位错 芯附近，并不倾向于沿位错线密集分布. 关键词铝镁合金；溶质原子；位错；扩散：最低能量路径 分类号TG111.6 Minimum energy path of a solute atom diffusing to an edge dislocation core in Al-Mg alloys based on empirical atomic potential LI Xiao-tong2),TANG Xiao-zhi,GUO Ya-fang 1)Institute of Engineering Mechanics,Beijing Jiaotong University,Beijing 100044,China 2)National Experimental Teaching Demonstration Center for Civil Engineering,Beijing Jiaotong University,Beijing 100044,China Corresponding author,E-mail:yfguo@bjtu.edu.en ABSTRACT Al-Mg alloys are widely used in manufacturing.But at specific temperatures and strain rates,their plastic instability is not conducive to processing applications.The microscopic mechanism of plastic instability is the interaction between solute atoms and dislocations which induce a pinning-unpinnning effect.This effect,reflected on the microscopic scale,is also called dynamic strain ag- ing (DSA).The DSA phenomenon causes negative strain-rate sensitivity and leads to plastic instability,which is harmful to its produc- tion.In this paper,the climbing image nudged elastic band method was adopted to explore the transition states along the minimum po- tential energy path,revealing a detailed evolution of atomic structures.The interaction range relies on the relative position and energy barrier of the transition,when a substitutional solute diffuses to an edge dislocation core in its stress field.Both substitution and vacan- cy-assisted migration are considered.The thermal activation time required for diffusion was estimated using transition state theory.The results indicate that there is no obvious law of solute atom migration in the compressive stress field.However,with the distance of the solute atom and the dislocation shortening,the migration potential energy barrier and the total energy of the system were gradually re- 收稿日期：2018-06-20 基金项目：中央高校基本科研业务费专项资金资助项目(2018RC019):国家自然科学基金资助项目(11602015,11772043)：北京交通大学大学 生科研训练资助项目(170130018)工程科学学报,第 41 卷,第 7 期:898鄄鄄905,2019 年 7 月 Chinese Journal of Engineering, Vol. 41, No. 7: 898鄄鄄905, July 2019 DOI: 10. 13374 / j. issn2095鄄鄄9389. 2019. 07. 008; http: / / journals. ustb. edu. cn 经验原子势下铝镁合金中溶质原子向位错芯迁移的最 低能量路径 李晓彤1,2) , 汤笑之1) , 郭雅芳1) 苣 1)北京交通大学土木建筑工程学院, 北京 100044 2) 北京交通大学土木工程国家级实验教学示范中心, 北京 100044 苣通信作者, E鄄mail: yfguo@ bjtu. edu. cn 摘 要 铝镁合金在制造业中应用广泛,但其在特定应变率下的塑性失稳不利于加工应用. 溶质原子与位错的交互作用是塑 性失稳的微观机理. 本文采用势能曲面过渡态搜索技术计算了铝镁合金中替代型溶质镁原子向位错芯迁移的过渡态,确认了 溶质原子与位错芯的交互作用范围,并采用过渡态理论估算了迁移扩散所需的时间,且区分了无空位及有空位参与迁移两种 情况. 结果表明,位错压应力区内的溶质原子迁移无明显规律,而在位错拉应力区内,随着溶质原子与位错间距的缩短,迁移 势能垒和系统总能量均逐渐降低. 说明目前广泛采用的经验原子势可以很好地反映溶质原子易朝位错拉应力区偏聚这一现 象. 溶质原子迁移的过渡态证实迁移过程中的微观结构变化因溶质原子所处位置不同而各异,而交互作用范围不超过约 2 nm. 空位参与对迁移的辅助作用被量化为迁移热激活时间的缩短,并得出其可在微秒量级. 当溶质原子完成迁移稳定至位错 芯附近,并不倾向于沿位错线密集分布. 关键词 铝镁合金; 溶质原子; 位错; 扩散; 最低能量路径 分类号 TG111郾 6 收稿日期: 2018鄄鄄06鄄鄄20 基金项目: 中央高校基本科研业务费专项资金资助项目(2018RC019);国家自然科学基金资助项目(11602015, 11772043);北京交通大学大学 生科研训练资助项目(170130018) Minimum energy path of a solute atom diffusing to an edge dislocation core in Al鄄鄄Mg alloys based on empirical atomic potential LI Xiao鄄tong 1,2) , TANG Xiao鄄zhi 1) , GUO Ya鄄fang 1) 苣 1) Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing 100044, China 2) National Experimental Teaching Demonstration Center for Civil Engineering, Beijing Jiaotong University, Beijing 100044, China 苣Corresponding author, E鄄mail: yfguo@ bjtu. edu. cn ABSTRACT Al鄄鄄Mg alloys are widely used in manufacturing. But at specific temperatures and strain rates, their plastic instability is not conducive to processing applications. The microscopic mechanism of plastic instability is the interaction between solute atoms and dislocations which induce a pinning鄄unpinnning effect. This effect, reflected on the microscopic scale, is also called dynamic strain ag鄄 ing (DSA). The DSA phenomenon causes negative strain鄄rate sensitivity and leads to plastic instability, which is harmful to its produc鄄 tion. In this paper, the climbing image nudged elastic band method was adopted to explore the transition states along the minimum po鄄 tential energy path, revealing a detailed evolution of atomic structures. The interaction range relies on the relative position and energy barrier of the transition, when a substitutional solute diffuses to an edge dislocation core in its stress field. Both substitution and vacan鄄 cy鄄assisted migration are considered. The thermal activation time required for diffusion was estimated using transition state theory. The results indicate that there is no obvious law of solute atom migration in the compressive stress field. However, with the distance of the solute atom and the dislocation shortening, the migration potential energy barrier and the total energy of the system were gradually re鄄