Yao Di, Deng Lei, Zhang Mao, Wang Xinyun, Tang Na, Li Jianjun
State Key Laboratory of Materials Processing and Die &Mould Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, 430074 Wuhan, Hubei, China.
Sci Rep. 2015 Jan 28;5:8083. doi: 10.1038/srep08083.
Size effect is of great importance in micro forming processes. In this paper, micro cylinder compression was conducted to investigate the deformation behavior of bulk metallic glasses (BMGs) in supercooled liquid region with different deformation variables including sample size, temperature and strain rate. It was found that the elastic and plastic behaviors of BMGs have a strong dependence on the sample size. The free volume and defect concentration were introduced to explain the size effect. In order to demonstrate the influence of deformation variables on steady stress, elastic modulus and overshoot phenomenon, four size-dependent factors were proposed to construct a size-dependent constitutive model based on the Maxwell-pulse type model previously presented by the authors according to viscosity theory and free volume model. The proposed constitutive model was then adopted in finite element method simulations, and validated by comparing the micro cylinder compression and micro double cup extrusion experimental data with the numerical results. Furthermore, the model provides a new approach to understanding the size-dependent plastic deformation behavior of BMGs.
尺寸效应在微成形过程中具有重要意义。本文通过微圆柱压缩试验，研究了块状金属玻璃（BMG）在过冷液相区的变形行为，涉及不同的变形变量，包括样品尺寸、温度和应变速率。研究发现，BMG的弹性和塑性行为强烈依赖于样品尺寸。引入自由体积和缺陷浓度来解释尺寸效应。为了阐明变形变量对稳态应力、弹性模量和过冲现象的影响，提出了四个尺寸相关因素，以基于作者先前根据粘度理论和自由体积模型提出的麦克斯韦脉冲型模型构建尺寸相关本构模型。然后将所提出的本构模型应用于有限元方法模拟，并通过将微圆柱压缩和微双杯挤压实验数据与数值结果进行比较来进行验证。此外，该模型为理解BMG的尺寸相关塑性变形行为提供了一种新方法。
