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Modeling and simulation of microstructural evolution in Zr based Bulk Metallic Glass Matrix Composites during solidification Muhammad Musaddique Ali Rafique1, Dong Qiu1, Mark Easton1 1

School of Engineering [Aerospace, Mechanical and Manufacturing Engineering], RMIT University, Queensbury Street, Carlton, 3053 VIC, AUSTRALIA

ABSTRACT Bulk metallic glass and their composites are unique new materials which have superior mechanical and structural properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from disadvantages of poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure on the application of force. Their behavior is dubious and requires extensive experimentation to draw conclusive results. In present study, an effort has been made to overcome this pitfall by simulation. A quantitative mathematical model based on KGT theory has been developed to describe nucleation and growth of second phase dendrites from melt in glassy matrix during solidification. It yields information about numerical parameters necessary to understand the behaviour of each individual element in multicomponent sluggish slurry and their effect on final microstructural evolution. Model is programmed and simulated in MATLAB®. Its validation is done by comparison with identical curves reported in literature previously for similar alloys. Results indicate that the effect of incorporating all heat transfer coefficients at macroscopic level and diffusion coefficients at microscopic level play a vital role in refining the model and bringing it closer to actual experimental observations. Two types of hypo and eutectic systems namely Zr65Cu15Al10Ni10 and Zr47.5Cu45.5Al5Co2 respectively were studied. Simulation results were found to be in good agreement with prior simulated and experimental values. INTRODUCTION Bulk Metallic Glasses [1] have emerged [2] as competitive structural engineering material [3] during last two decades and have attracted the attention of several major research groups [4-18] around the word to further probe into the science and engineering behind their formation [19], microstructural evolution [20], property development and structure – property relationship [21, 22]. Main areas of focus have been investigation of evolution of mechanical properties in these materials as despite their high hardness and very high elastic strain limit, they do not exhibit any tensile ductility and fail catastrophically [23, 24] under tensile and impact loading. This happens due to rapid movement of shear bands [25-32] in the volume of materials by virtue of which material does not exhibit any yielding. Infact, they exhibit strain softening rather than strain hardening upon deformation in tensile loading [33-35]. These behaviors render them useless in practical structural engineering applications [36, 37]. In addition to that, they are limited by the size in which 100% monolithic glassy struc