Structural and mechanical characterization of heterogeneities in a CuZr-based bulk metallic glass processed by high pressure torsion
Structural and mechanical characterization of heterogeneities in a CuZr-based bulk metallic glass processed by high pressure torsion
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DOI：
10.1016/j.actamat.2018.08.032
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发表时间：
2018-11-01
期刊：
影响因子：
9.4
通讯作者：
Rentenberger, Christian
中科院分区：
文献类型：
--
作者：
Ebner, Christian;Escher, Benjamin;Rentenberger, Christian
采用同步辐射X射线衍射、纳米压痕、差示扫描量热、原子力和透射电子显微镜等方法对不同条件下高压扭转（HPT）制备的Cu45Zr45Al5Ag5大块金属玻璃样品进行了表征。实验结果清楚地表明，HPT通过增加平均原子体积来改变非晶结构。与过剩平均原子体积相关的复兴水平在较高的剪切应变下得到增强，这是从弛豫弛豫曲线推断的。通过映射的结构和力学量，应变引起的再生状态的特点是横截面HPT样品上的局部规模。得到了弹性软化与塑性软化之间以及软化与过剩平均原子体积之间的明确相关性。但也揭示了HPT引起的再生的不均匀性，导致在变形较小的区域旁边形成高度应变软化的区域。高达20%的硬度下降与高达0.75%的平均原子体积的估计增加相关联。基于同步辐射X射线衍射和纳米压痕测量，可以得出结论，弹性波动增强的再生材料在不同的长度尺度下到原子尺度。此外，计算的柔性体积和相应的平均均方原子位移增加。纳米压痕过程中的塑性响应表明，HPT处理促进了更类似的变形。(C)2018 Acta Materialia Inc.出版社：Elsevier Ltd
Cu45Zr45Al5Ag5 bulk metallic glass samples, processed by high pressure torsion (HPT) under various conditions, were characterized using synchrotron X-ray diffraction, nanoindentation, differential scanning calorimetry, atomic force and transmission electron microscopy. The experimental results clearly show that HPT modifies the amorphous structure by increasing the mean atomic volume. The level of rejuvenation, correlated with the excess mean atomic volume, is enhanced at higher shear strains as inferred from relaxation enthalpies. By mapping of structural and mechanical quantities, the strain induced rejuvenated state is characterized on cross-sectional HPT samples on a local scale. A clear correlation both between elastic and plastic softening and between softening and excess mean atomic volume is obtained. But also the heterogeneity of the HPT induced rejuvenation is revealed, resulting in the formation of highly strain-softened regions next to less-deformed ones. A hardness drop of up to 20% is associated with an estimated increase of the mean atomic volume of up to 0.75%. Based on synchrotron X-ray diffraction and nanoindentation measurements it is concluded that elastic fluctuations are enhanced in the rejuvenated material on different length scales down to atomic scale. Furthermore, the calculated flexibility volume and the corresponding average mean square atomic displacement is increased. The plastic response during nanoindentation indicates that HPT processing promotes a more homogeneous-like deformation. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd.