Despite a wealth of experimental studies focused on determining and improving mechanical properties and development of fundamental understanding of underlying mechanisms behind nucleation and growth of ductile phase p...Despite a wealth of experimental studies focused on determining and improving mechanical properties and development of fundamental understanding of underlying mechanisms behind nucleation and growth of ductile phase precipitates from melt in glassy matrix, still, there is dearth of knowledge about how these ductile phases nucleate during solidification. Various efforts have been made to address this problem such as experiments in microgravity, high resolution electron microscopy and observation in synchrotron light after levitation but none have proved out to be satisfactory. In this study, an effort has been made to address this problem by modelling and simulation. Current state of the art of development, manufacturing, characterisation and modelling and simulation of bulk metallic glass matrix composites is described in detail. Evolution of microstructure in bulk metallic glass matrix composites during solidification in additive manufacturing has been presented with the aim to address fundamental problem of evolution of solidification microstructure as a result of solute partitioning, diffusion and capillary action. An overview is also presented to explain the relation of microstructure evolution to hardness and fracture toughness. This is aimed at overcoming fundamental problem of lack of ductility and toughness in this diverse class of materials. Quantitative prediction of solidification microstructure is done with the help of advanced part scale modelling and simulation techniques. It has been systematically proposed that 2-dimensional cellular automaton (CA) method combined with finite element (for thermal modelling) tools (CA-FE) programmed on FORTRAN? and parallel simulated on ABAQUS? would best be able to describe this complicated multiphysics phenomenon in most efficient way. Focus is laid on quantification of methodology by which modelling and simulation can be adopted and applied to describe evolution of microstructure in this important class of materials. It is found that proposed methodology is meritorious.展开更多
Bulk metallic glass matrix composites (BMGMC) are unique materials of future having excellent mechanical properties (such as high hardness, strength and profound elastic strain limit). However, they exhibit poor ducti...Bulk metallic glass matrix composites (BMGMC) are unique materials of future having excellent mechanical properties (such as high hardness, strength and profound elastic strain limit). However, they exhibit poor ductility and suffer from catastrophic failure on the application of force. The reasons behind this are still not very well understood. In this study, an effort has been made to overcome this pitfall by solidification processing. Zr based BMGMCs are produced in the form of “as cast” wedges using vacuum arc melting and suction casting button furnace. The idea is to study the effect of cooling rate and inoculation on formability during solidification. Adjustment, manipulation and proper control of processing parameters are observed to reflect upon the quality of ingots such as improved castability, proper mold filling and defect free casting as characterized by NDT. Further, thermal analysis, optical microscopy and hardness measurement confirmed the formation and evolution of in-situcomposite structure. This is first footprint of pathway towards sustainable manufacturing of these alloys in future.展开更多
After a silence of three decades, bulk metallic glasses and their composites have re-emerged as a competent engineering material owing to their excellent mechanical properties not observed in any other engineering mat...After a silence of three decades, bulk metallic glasses and their composites have re-emerged as a competent engineering material owing to their excellent mechanical properties not observed in any other engineering material known till date. However, they exhibit poor ductility and little or no toughness which make them brittle and they fail catastrophically under tensile loading. Exact explanation of this behaviour is difficult, and a lot of expensive experimentation is needed before conclusive results could be drawn. In present study, a theoretical approach has been presented aimed at solving this problem. A detailed mathematical model has been developed to describe solidification phenomena in zirconium based bulk metallic glass matrix composites during additive manufacturing. It precisely models and predicts solidification parameters related to microscale solute diffusion (mass transfer) and capillary action in these rapidly solidifying sluggish slurries. Programming and simulation of model is performed in MATLAB®. Results show that the use of temperature dependent thermophysical properties yields a synergic effect for multitude improvement and refinement simulation results. Simulated values proved out to be in good agreement with prior simulated and experimental results.展开更多
Bulk metallic glass and their composites (BMGMCs) are a new class of materials which possess superior mechanical properties as compared to existing conventional materials. Owing to this, they are potential candidates ...Bulk metallic glass and their composites (BMGMCs) are a new class of materials which possess superior mechanical properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure under applied force. Their behavior is dubious, unpredictable and requires extensive experimentation to arrive at conclusive results. In present study, an effort has been made to design bulk metallic glass matrix composites by the use of modeling and simulation. A probabilistic cellular automaton (CA) model is developed and described in present study by author which is used in conjunction with earlier developed deterministic model to predict microstructural evolution in Zr based BMGMCs in additive manufacturing liquid melt pool. It is elaborately described with an aim to arrive at quantitative relations which describe process and steps of operations. Results indicate that effect of incorporating all mass transfer and diffusion coefficients under transient conditions and precise determination of probability number play a vital role in refining the model and bringing it closer to a level that it could be compared to actual values. It is shown that proposed tailoring can account for microstructural evolution in metallic glasses.展开更多
Bulk metallic glass matrix composites have emerged as a new potential material for structural engineering applications owing to their superior strength, hardness and high elastic strain limit. However, their behaviour...Bulk metallic glass matrix composites have emerged as a new potential material for structural engineering applications owing to their superior strength, hardness and high elastic strain limit. However, their behaviour is dubious. They manifest brittleness and inferior ductility which limit their applications. Various methods have been proposed to overcome this problem. Out of these, introduction of foreign particles (inoculants) during solidification has been proposed as the most effective. In this study, an effort has been made to delimit this drawback. A systematic tale has been presented which explains the evolution of microstructure in Zr47.5Cu45.5Al5Co2 and Zr65Cu15Al10Ni10 bulk metallic glass matrix composites with varying percentage of ZrC inoculant as analysed by secondary electron, back scatter electron imaging of “as cast” unetched samples and indentation microhardness testing. Secondary electron imaging of indents was also performed which shows development of shear transformation zones at edges of square of indents. Mostly, no cracking was observed, few cracks bearing Palmqvist morphology were witnessed in samples containing lower percentage of inoculant. A support is provided to hypothesis that inoculations remain successful in promoting phase formation and crystallinity and improving toughness.展开更多
文摘Despite a wealth of experimental studies focused on determining and improving mechanical properties and development of fundamental understanding of underlying mechanisms behind nucleation and growth of ductile phase precipitates from melt in glassy matrix, still, there is dearth of knowledge about how these ductile phases nucleate during solidification. Various efforts have been made to address this problem such as experiments in microgravity, high resolution electron microscopy and observation in synchrotron light after levitation but none have proved out to be satisfactory. In this study, an effort has been made to address this problem by modelling and simulation. Current state of the art of development, manufacturing, characterisation and modelling and simulation of bulk metallic glass matrix composites is described in detail. Evolution of microstructure in bulk metallic glass matrix composites during solidification in additive manufacturing has been presented with the aim to address fundamental problem of evolution of solidification microstructure as a result of solute partitioning, diffusion and capillary action. An overview is also presented to explain the relation of microstructure evolution to hardness and fracture toughness. This is aimed at overcoming fundamental problem of lack of ductility and toughness in this diverse class of materials. Quantitative prediction of solidification microstructure is done with the help of advanced part scale modelling and simulation techniques. It has been systematically proposed that 2-dimensional cellular automaton (CA) method combined with finite element (for thermal modelling) tools (CA-FE) programmed on FORTRAN? and parallel simulated on ABAQUS? would best be able to describe this complicated multiphysics phenomenon in most efficient way. Focus is laid on quantification of methodology by which modelling and simulation can be adopted and applied to describe evolution of microstructure in this important class of materials. It is found that proposed methodology is meritorious.
文摘Bulk metallic glass matrix composites (BMGMC) are unique materials of future having excellent mechanical properties (such as high hardness, strength and profound elastic strain limit). However, they exhibit poor ductility and suffer from catastrophic failure on the application of force. The reasons behind this are still not very well understood. In this study, an effort has been made to overcome this pitfall by solidification processing. Zr based BMGMCs are produced in the form of “as cast” wedges using vacuum arc melting and suction casting button furnace. The idea is to study the effect of cooling rate and inoculation on formability during solidification. Adjustment, manipulation and proper control of processing parameters are observed to reflect upon the quality of ingots such as improved castability, proper mold filling and defect free casting as characterized by NDT. Further, thermal analysis, optical microscopy and hardness measurement confirmed the formation and evolution of in-situcomposite structure. This is first footprint of pathway towards sustainable manufacturing of these alloys in future.
文摘After a silence of three decades, bulk metallic glasses and their composites have re-emerged as a competent engineering material owing to their excellent mechanical properties not observed in any other engineering material known till date. However, they exhibit poor ductility and little or no toughness which make them brittle and they fail catastrophically under tensile loading. Exact explanation of this behaviour is difficult, and a lot of expensive experimentation is needed before conclusive results could be drawn. In present study, a theoretical approach has been presented aimed at solving this problem. A detailed mathematical model has been developed to describe solidification phenomena in zirconium based bulk metallic glass matrix composites during additive manufacturing. It precisely models and predicts solidification parameters related to microscale solute diffusion (mass transfer) and capillary action in these rapidly solidifying sluggish slurries. Programming and simulation of model is performed in MATLAB®. Results show that the use of temperature dependent thermophysical properties yields a synergic effect for multitude improvement and refinement simulation results. Simulated values proved out to be in good agreement with prior simulated and experimental results.
文摘Bulk metallic glass and their composites (BMGMCs) are a new class of materials which possess superior mechanical properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure under applied force. Their behavior is dubious, unpredictable and requires extensive experimentation to arrive at conclusive results. In present study, an effort has been made to design bulk metallic glass matrix composites by the use of modeling and simulation. A probabilistic cellular automaton (CA) model is developed and described in present study by author which is used in conjunction with earlier developed deterministic model to predict microstructural evolution in Zr based BMGMCs in additive manufacturing liquid melt pool. It is elaborately described with an aim to arrive at quantitative relations which describe process and steps of operations. Results indicate that effect of incorporating all mass transfer and diffusion coefficients under transient conditions and precise determination of probability number play a vital role in refining the model and bringing it closer to a level that it could be compared to actual values. It is shown that proposed tailoring can account for microstructural evolution in metallic glasses.
文摘Bulk metallic glass matrix composites have emerged as a new potential material for structural engineering applications owing to their superior strength, hardness and high elastic strain limit. However, their behaviour is dubious. They manifest brittleness and inferior ductility which limit their applications. Various methods have been proposed to overcome this problem. Out of these, introduction of foreign particles (inoculants) during solidification has been proposed as the most effective. In this study, an effort has been made to delimit this drawback. A systematic tale has been presented which explains the evolution of microstructure in Zr47.5Cu45.5Al5Co2 and Zr65Cu15Al10Ni10 bulk metallic glass matrix composites with varying percentage of ZrC inoculant as analysed by secondary electron, back scatter electron imaging of “as cast” unetched samples and indentation microhardness testing. Secondary electron imaging of indents was also performed which shows development of shear transformation zones at edges of square of indents. Mostly, no cracking was observed, few cracks bearing Palmqvist morphology were witnessed in samples containing lower percentage of inoculant. A support is provided to hypothesis that inoculations remain successful in promoting phase formation and crystallinity and improving toughness.
