Fracture Morphology and Local Deformation Characteristics in the Metallic Glass Matrix Composite Under Tension
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INTRODUCTION
BULK metallic glasses (BMGs) have attracted intense attentions for the incomparable mechanical properties, e.g., excellent elastic limits, high strengths, and high hardness.[1–5] However, due to the unlimited propagation of highly local shear bands, BMGs always display limited plastic deformation in compression and nearly zero plasticity in tension, seriously retarding their engineering applications. To circumvent this disadvantage, metallic glass matrix (MGM) composites containing ex situ or in situ phase were designed with improved toughness and the considerable tensile plasticity at room temperature. In these alloys, MGM composites containing in situ ductile dendritic crystalline phases have gained widespread achievements for sharing the large plastic deformation of dendrites and high strength of the glass phase,[5–11] e.g., Ti-,[2,6] Zr-,[3,5,7,8] Cu-based,[11] and Mg-[10] MGM composites. Up to now, researches including the microstructure, mechanical properties, as well as deformation mechanisms of MGM composites have been carried out extensively. It is found that mechanical properties rely on the microstructures,[12–16] e.g., dendrite size, volume fraction, spacing, morphology, etc. In terms of the micro-mechanisms, many results have been reported
Y.S. WANG and J.W. QIAO, Researchers, and X.H. SUN, Student, 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 e-mail:[email protected] G.J. HAO, Y. ZHANG, and J.P. LIN, Researchers, are with the State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, P.R. China. Z.X. GUO, Student, and M.L. SUI, Researcher, are with the Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, P.R. China. Manuscript submitted May 12, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
experimentally and theoretically. The plastic deformation occurred first within b-crystal by formation of slip bands.[3,4,7,14] The multiplication of slip bands and shear bands is favorable to the macro-plasticity, but the cracks would be initiated at those deepened deformation bands as the deformation proceeds, leading to the final failure.[7,14] The fragmentation of the b-crystal phase rather than crystallization within the glass matrix contributes to the high-tensile ductility.[9] A tensile deformation model on the basis of elastic-plastic-damage process was proposed according to the work-hardening behavior of dendrites and softening of the glass matrix.[10] The tensile necking behavior occurred in b-crystal for the intrinsic low work-hardening rate of the b-crystal under the tensile loading.[12,13] Based on the large scale atomistic simulations, plastic shearing events were confined in local glass matrix.[15] Moreover, the interaction between the two phases refers to the lattice sliding and the local shear transaction zone.[
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