摘要
利用Z衬度成像技术研究了两种耐热镁合金Mg_(97)Zn_1Y_2与Mg_(97)Zn_1Gd_2(at.%)中的位错。塑性变形过程中形成的倾侧晶界上周期性分布的基面〈a〉位错分解形成层错,伴随合金元素在层错上富集可以形成类似长周期堆垛的结构,能够钉扎晶界并抑制晶界高温软化。随着应变量增加,观察到了基面〈a〉位错与锥面〈c+a〉位错构成的复合倾侧晶界,以及单纯由〈c+a_(60)〉位错或〈c+a_s〉位错重排构成的晶界,表明开动了〈c+a〉锥面滑移系,有利于协调材料变形。合金元素在位错处偏聚形成柯垂尔气团,可以强化材料。热变形过程中Gd元素在Mg基体内位错的张应变区富集形成柯垂尔气团,加速β′-Mg_7Gd柱面析出相的异质形核生长。
Dislocations in two heat-resistant Mg alloys, Mg_（97）Zn_1Y_2 and Mg_（97）Zn_1Gd_2（at.%）, were studied using aberration-corrected Z-contrast imaging techniques. Dissociation of basal 〈a〉 dislocations and associated segregation of solute atoms produced local structures like long-periodic stacking ordered phases at tilt GBs formed during plastic deformation, which may play an important role in both pinning the GBs and preventing them from softening at elevated temperatures. GBs composed of 〈c＋a〉 dislocations were formed due to the activation of pyramidal slip systems with increasing plastic strain. Pyramidal slip of 〈c＋a〉 dislocations is important for ductility of Mg alloys. Solute segregation along dislocations in the form of Cottrell atmospheres during hot deformation, not only plays an important role in strengthening by directly impeding dislocation motion, but also facilitates heterogeneous nucleation and growth of strengthening precipitates. These findings about dislocations provide insights on the strengthening and toughening mechanisms in Mg alloys.
作者
杨志卿
胡伟伟
叶恒强
YANG Zhi-qing;HU Wei-wei;YE Heng-qiang(Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang Liaoning 110016,China)
出处
《电子显微学报》
CAS
CSCD
北大核心
2018年第5期481-489,共9页
Journal of Chinese Electron Microscopy Society
基金
国家自然科学基金资助项目(Nos.51390473
51771202)
中国科学院前沿重点项目(No.QYZDY-SSW-JSC027)
关键词
位错
柯垂尔气团
铃木偏聚
析出形核
像差校正电子显微学
dislocation
Cottrell atmosphere
Suzuki segregation
nucleation
aberration-corrected electron microscopy
