温度对纳米孪晶Al强化和软化行为的影响  

Effect of temperature on strengthening and softening behavior of nanotwinned Al

作　　者：牛媛 侯兆阳[1] 王凤龙 李昌 高全华[1] 邹鹏飞 高磊 NIU Yuan;ZHAO Yang-hou;WANG Feng-long;LI Chang;GAO Quan-hua;ZOU Peng-fei;GAO Lei(School of Science,Chang’an University,Xi’an 710064,China)

机构地区：[1]长安大学理学院,西安710064

出　　处：《中国有色金属学报》2023年第9期2813-2824,共12页The Chinese Journal of Nonferrous Metals

基　　金：国家自然科学基金资助项目(51771033);中央高校基本科研业务费专项资助(300102122201)。

摘　　要：纳米晶金属的超高强度和良好拉伸延展性的结合可以通过引入孪晶来实现,但温度对孪晶间距降低过程的强化-软化转变仍缺乏系统研究。本文采用分子动力学模拟方法考察了温度对纳米孪晶Al强化和软化行为的影响。结果表明:纳米孪晶Al变形过程存在临界温度T_(s),当加载温度高于临界温度T_(s)时,随着孪晶间距的减少,纳米孪晶Al的强度呈现强化-软化转变的现象;当加载温度低于临界温度T_(s)时,呈现持续强化现象;而且随着晶粒尺寸的增大,发生持续强化的临界温度T_(s)升高。进一步研究表明,纳米孪晶Al在高温下(T>T_(s))下的强化-软化转变机理与纳米孪晶Cu一致,是由不同的位错发射机制引起,位错由倾斜于孪晶界方向发射逐渐转变为平行于孪晶界方向发射;在低温下(T<T_(s))的变形过程中,只有极少位错被激发,此时的持续强化行为由应变局域化主导,不同于纳米孪晶Cu在低温下的位错机制。The high strength and excellent ductility of nanocrystalline metals can be realized by introducing the twin structure,while the effect of temperature on decreasing twin spacing is not clear,which should be further studied.In this paper,the deformation processes of nanotwinned Al with different twin spacing were simulated by molecular dynamics method.The mechanical behavior and deformation mechanism of nanotwinned Al with higher fault energy under different temperatures were investigated,and the influence of temperature on the strengthening and softening behavior of nanotwinned Al was clarified.The results show that there exists a critical temperature T_(s)in the deformation of nanotwinned Al.When the tensile temperature is higher than the critical temperature T_(s),the strengthening-softening transition occurs with the decrease of twin spacing.When the tensile temperature is lower than the critical temperature T_(s),continuous strengthening occurs.Moreover,the critical temperature T_(s)for continuous strengthening increases with the increase of grain size.Further study shows that the mechanism of strengthening-softening transition at high temperature(T>T_(s))is consistent with that in nanotwinned Cu,which is also caused by different dislocation emission mechanisms.The dislocation emission gradually changes from the direction inclined to twin boundaries to parallel to twin boundaries.In the deformation processes of nanotwinned Al at low temperature(T<T_(s)),very few dislocations are excited.The mechanism of continuous strengthening behavior is dominated by strain localization,which is different from the dislocation mechanism in nanotwinned Cu at low temperature.

关 键 词：纳米孪晶Al 分子动力学模拟 力学行为 变形机制 

分 类 号：TF11.31[冶金工程—冶金物理化学]