Plastic flow softening in a bulk metallic glass
Plastic flow softening in a bulk metallic glass
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DOI：
10.1016/j.actamat.2006.05.011
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发表时间：
2006-09-01
期刊：
影响因子：
9.4
通讯作者：
Ramamurty, U.
中科院分区：
文献类型：
--
作者：
Bhowmick, R.;Raghavan, R.;Ramamurty, U.
对非晶态金属塑性变形过程中产生的过量自由体积在应变软化中的作用进行了实验研究。采用球形压痕法在锆基块体非晶合金（BMG）结合界面上形成了一个边界清晰的大塑性区。变形区的弹性模量和硬度映射通过纳米压痕进行。实验观察表明，从变形区获得的载荷P与穿透深度h的关系曲线装饰有离散的位移跳跃，否则在未变形的材料中不存在。大压头下的变形区也比远离压头的变形区软。一个简单的和近似的分析表明，应变软化的BMG是有关的多余的自由体积，是在先前的变形过程中创建。与一般预期相反，变形材料的差示扫描量热法表明自由体积减小。这些结果可以通过假设由于过量自由体积的聚结而形成纳米空隙来解释。这些纳米空隙反过来降低了通过剪切带塑性变形所需的应力，这导致观察到硬度降低。(c)2006 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
An experimental investigation into the role of the excess free volume that is created during plastic deformation in strain softening of amorphous metals was conducted. A well-defined and large plastic zone was created through the spherical indentation of a bonded interface of a Zr-based bulk metallic glass (BMG). Elastic modulus and hardness mapping of the deformation zone was conducted through nanoindentation. Experimental observations show that the load, P, vs. depth of penetration, h, curves obtained from the deformation zone are decorated with discrete displacement jumps, which are otherwise absent in the undeformed material. The prior-deformed zone underneath the large indenter was also found to be softer than that far away from the indenter. A simple and approximate analysis shows that the strain softening of the BMG is related to the excess free volume that is created during prior deformation. Contrary to general expectation, differential scanning calorimetry of the deformed material indicates a reduced free volume. These results can be explained by postulating the formation of nanovoids due to the coalescence of the excess free volume. These nanovoids, in turn, lower the stress required for plastic deformation through shear bands, which leads to the observation of reduced hardness. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.