Volume 39, Issue 3 (Journal of Advanced Materials-Fall 2020)
2020, 39(3): 129-140 |
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Department of Materials Engineering and Metallurgy, Shahid Bahonar University of Kerman, Kerman, Iran. , mtasadi@uk.ac.ir
Abstract: (2237 Views)
In this study, the influence of temperature and strain rate on plastic flow of a Zr-based bulk metallic glass (BMG) during the three-point bending test was studied to find a correlation between strain rate sensitivity (m) and flow behavior. The flexural stress-deflection curves revealed two distinct types of dynamics, serrated and non-serrated flow, related to temperature and strain rate. The serrated flow which appeared at temperatures higher than a critical value or strain rates lower than a critical value, was simultaneously due to activation of shear transformation zones (STZs) and time-dependent structural relaxations. Further results indicated negative and positive values of m at temperatures above and below 0.4 Tg, respectively. The main reason for negative strain rate sensitivity was insufficient time of structural relaxation at high strain rates which lead to generation of free volume inside shear bands making the BMG softer. Comparison of STZ activation energy with activation energy for the onset of serration indicated almost equal values and there was a close relationship between serrated flow and STZ operation.
Keywords: Bulk metallic glass, Strain rate sensitivity, Shear transformation zone, Serrated flow, Structural relaxation.
Type of Study: Research |
Subject:
Forming and mechanical properties
Received: 2020/07/22 | Accepted: 2020/12/19 | Published: 2020/12/20
Received: 2020/07/22 | Accepted: 2020/12/19 | Published: 2020/12/20