Tensile Mechanical Behaviors of In Situ Metallic Glass Matrix Composites at Ambient Temperature and in Supercooled Liqui
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I.
INTRODUCTION
THE discovery of metallic glasses triggered a flood of research on bulk metallic glasses (BMGs), as BMGs exhibit superior performances at ambient temperature, such as excellent hardness, strength, stiffness, and corrosion resistance.[1,2] However, BMGs suffer from a strong tendency toward shear localization upon loading, which results in macroscopically-brittle failure at ambient temperature.[2] Poor tensile ductility and toughness restrict BMGs for structural engineering applications. Various approaches have been explored, aiming to improve the general plasticity of BMGs.[3,4] One of the most effective methods is to develop a series of in situ dendrite-reinforced metallic glass matrix composites (MGMCs), which have been developed by in situ introduction of secondary phases, such as particles, fibers, and skeletons.[5–8] The poor ductility of BMGs is attributed to the inhomogeneous deformation and highly localized shear bands.[9] But the secondary phase acts as a barrier to hinder the rapid propagation of shear bands and enables their interactions and multiplications, avoiding an early failure.[10] So in situ MGMCs exhibit improved room-temperature ductility and toughness,
T. ZHANG, Graduate Student, J.Y. SHI, Professor, J.W. QIAO, Associate Professor, and H.J. YANG, Lecturer, are with the Laboratory of Applied Physics and Mechanics of Advanced Materials, College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, P.R. China. Contact emails: Shijuyan@ tyut.edu.cn; [email protected] P.K. LIAW, Professor, is with Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996-2200. Manuscript submitted April 3, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS A
compared with monolithic BMGs, macroscopically characterized by the generation of multiple-shear bands.[11] To the authors’ knowledge, intensive studies on mechanical behaviors of in situ MGMCs have proceeded under compressive loading. In contrast, there are scarce reports on tension for in situ MGMCs. Due to difficulties in preparing the tensile specimen, such as formation of defects by suction casting, low success rates, and poor repeatability of tensile experiments, and complexity in machining etc. But for structural applications, the materials under tension are widely present. Furthermore, service temperatures of materials are not only at room temperature but also at high temperatures. Studying the tensile properties at ambient and high temperatures is extremely important. In the present study, in situ dendrite-reinforced Ti-based MGMCs with the atomic composition of Ti40Zr24V12Cu5Be19 have been prepared, which exhibit large room-temperature ductility, compared with the monolithic BMGs. At supercooled liquid region [613 K (340 C)], superplastic homogeneous deformation, which is the feature of monolithic BMGs,[12,13] is not observed. While at 613 K (340 C), the yield strength of the composites is higher than the conventional titanium alloys, as well as common engineering m
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