Serration Behavior of a Zr-Based Metallic Glass Under Different Constrained Loading Conditions
- PDF / 1,893,250 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 29 Downloads / 178 Views
INTRODUCTION
THE plastic behavior of metallic glasses (MGs) has been studied as a long-term topic for both scientific and engineering interest. At room temperature, MGs deform by localized flow in shear bands.[1–4] With such deformation manner, the plastic behaviors of MGs depend on not only the material but also the loading condition, such as stress state (compression, tension, or bending[3–6]), temperature,[7,8] loading rate,[8,9] sample size,[10] and external constraint.[11] Especially, the plasticity of MGs could be greatly improved under constraint loading and in small-sized samples,[12–15] which provides an approach for MGs to achieve better properties. Experiments have revealed that under constrained loading condition, finer and denser shear bands could form due to the depression of shear band sliding.[11,12,16] However, it is still of concern how the shear band dynamics is altered with external constraint and how to better understand the improved plasticity of MGs under constrained loading conditions. In recent years, statistical analysis of the serration pattern has been used to understand the shear band dynamics in MGs.[1] Here the serrations refer to the
G.N. YANG, J.L. GU, and S.Q. CHEN, Ph.D. Students, Y. SHAO, Assistant Professor, and K.F. YAO, Professor, are with the School of Material Science and Engineering, Tsinghua University, Beijing, 100084, P.R. China, and also with the Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing, 100084, People’s Republic of China. Contact emails: [email protected], [email protected], [email protected] H. WANG, Professor, is with the Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen, 518060, P.R. China. Manuscript submitted February 23, 2016. Article published online August 31, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
repeated jerky stress drops on the loading curves, formed by avalanche and arrest of shear bands during MG deformation. The serration pattern (statistics of serrations of different magnitudes) indicates the shear bands in plastic and brittle MGs would follow selforganized critical (SOC) and chaotic dynamics, respectively.[17] By such understanding, the different plasticity and shear band dynamics in some MG systems[17–19] and under different loading rates[20–22] have been reasonably explained. However, statistical studies of serrations in MGs under constrained loading are still rare but important. In this work, the plastic behavior of a typical Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 MG with aspect ratios (length:diameter) of 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, and 3:1 was explored by uniaxial compression tests. A smaller aspect ratio could represent a higher degree of constraint. Improved plasticity and changed serration patterns were observed in the samples with smaller aspect ratio. Statistics analysis of the serration patterns indicated that in this Zr-based MG, the small stressdrop serrations and large stress-drop serrations follow SOC and chaotic dynamics, respectively. With decre
Data Loading...
