摘要
通过低能离子辐照,金属玻璃中会产生类似空位的微观结构缺陷,称为准空位.论文基于分子动力学模拟,研究了引入准空位的Cu50Zr50金属玻璃在单轴拉伸下的塑性变形行为,讨论了准空位的体积分数、分布区域对金属玻璃增韧效果的影响,探究了准空位在不同循环载荷作用下对金属玻璃的增韧效果.研究结果表明:引入准空位可以有效地增强金属玻璃的韧性;随准空位体积分数的增大,金属玻璃的变形模式发生了从脆性剪切破坏到均匀塑性变形的明显转变,使金属玻璃发生韧脆转变的临界准空位体积分数约为0.5%;准空位分布范围更广时,增韧效果更好;在循环载荷作用下,准空位的引入对金属玻璃韧性的提高仍然明显,当拉伸应变达到30%时,依旧能观察到非常均匀的塑性变形.对于一般的金属和合金,辐照引入的空位和间隙原子以及由此进一步演化形成的孔洞、析出相、位错环或层错四面体通常使得材料更加脆化.然而,对于金属玻璃而言,辐照形成的空位不易扩散和进一步演化,反而可能增加该材料的韧性.
To consider the effect of low-energy ion irradiation on metallic glasses(MGs), the vacancy-like defect which we call ‘quasi-vacancy’ is introduced in the material. By means of molecular dynamics simulations, the plastic deformation behavior of Cu50 Zr50 MGs with embedded quasi-vacancies is investigated carefully in this study. The influences of various parameters, such as the quasi-vacancy fraction and distribution, are also discussed systematically. It is found that a clear transition in the deformation mode from localized shear banding to homogeneous plastic flow may occur after the introduction of quasi-vacancies in the MGs. The intrinsic mechanism may be the decrease of short-to-medium-range structural order due to the injection of quasi-vacancies, which induces the increase in resistance against strain localization. The critical fraction of quasi-vacancies for the brittle-ductile transition is found to be 0.5%, only above which the MG can turn to be ductile. In addition, for a given quasi-vacancy fraction, a more homogeneous distribution of quasi-vacancies can lead to a better toughening effect. It is also observed that the toughening effect on MGs by introducing quasi-vacancies can be well maintained even after several cycles of tensile-compressive loading. These results can provide a microscopic understanding of the toughening effect of irradiation-induced quasi-vacancies on MGs, which may further shed light on the fabrication of MG materials with enhanced ductility.
作者
周志昆
朱笔达
黄敏生
Zhikun Zhou;Bida Zhu;Minsheng Huang(Department of Mechanics,Huazhong University of Science and Technology,Wuhan,430074;Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment,Wuhan,430074)
出处
《固体力学学报》
CAS
CSCD
北大核心
2020年第2期182-192,共11页
Chinese Journal of Solid Mechanics
基金
国家自然科学基金项目(11572136,11822204)资助。
关键词
金属玻璃
准空位
增韧
剪切带
分子动力学
metallic glass
quasi-vacancy
toughening
shear band
molecular dynamics
