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Z. Fan - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic predictions of mg al m m zn mn si alloy compositions amenable to Semisolid Metal processing
Materials Science and Technology, 2004Co-Authors: Y Q Liu, A Das, Z. FanAbstract:AbstractThe growing importance of Semisolid Metal processing and magnesium alloys for producing automotive components necessitate the development of new alloys that can take full advantage of this processing technique. Such alloy development can significantly benefit from prior predictions through computational thermodynamics in order to minimise time and cost intensive experiments based on the conventional trial and error approach. In the present work, a thermodynamic approach is undertaken to study the effects of the variations of alloy compositions in the Mg rich corner of the Mg - Al and Mg - Al - M (M = Zn, Mn, Si) systems on the Semisolid processability and properties. The influences of different alloying elements are compared and potential alloy compositions amenable to Semisolid Metal processing are presented.
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Semisolid Metal processing
International Materials Reviews, 2002Co-Authors: Z. FanAbstract:AbstractSemisolid Metal (SSM) processingis a relatively new technology for Metal forming. Different from the conventional Metal forming technologies which use either solid Metals (solid state processing) or liquid Metals (casting) as starting materials, SSM processing deals with Semisolid slurries, in which non-dendritic solid particles are dispersed in a liquid matrix. Semisolid Metal slurries exhibit distinctive rheological characteristics: the steady state behaviour is pseudoplastic (or shear thinning), while the transient state behaviour is thixotropic. All the currently available technologies for SSM processing have been developed based on those unique rheological properties, which in turn originate from their non-dendritic microstructures. Year 2001 marks the 30th anniversary of the concept of SSM processing. Today, SSM processing has established itself as a scientifically sound and commercially viable technology for production of Metallic components with high integrity, improved mechanical properti...
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modelling of rheological behaviour of Semisolid Metal slurries part 1 theory
Materials Science and Technology, 2002Co-Authors: J Y Chen, Z. FanAbstract:AbstractIn this paper, part of a series, a microstructural model is presented which describes the rheological behaviour of liquid-like Semisolid Metal (SSM) slurries under a simple shearing flow. A liquid-like SSM slurry is considered as a suspension in which interacting spherical solid particles of low cohesion are dispersed in a liquid matrix. In a simple shear flow field, the dynamic interactions between solid particles result in the formation of agglomerates. Under viscous forces, collisions between agglomerates lead to the formation of new agglomerates of a larger size, and at the same time agglomerates also break up giving rise to agglomerates of a smaller size. At a particular time, the state of agglomeration is described by a structural parameter n, which is defined as the average number of particles in the agglomerates. It is believed that it is the state of agglomeration which determines the rheological properties of SSM slurries, whereas the external flow conditions, such as shear rate and shea...
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modelling of rheological behaviour of Semisolid Metal slurries part 2 steady state behaviour
Materials Science and Technology, 2002Co-Authors: Z. Fan, J Y ChenAbstract:AbstractIn this part of the current series, the rheological model presented in Part 1 is applied to study the steady state behaviour of Semisolid Metal (SSM) slurries. Experimental results on the steady state viscosity of Sn–15 wt-%Pb slurries in the literature are used to determine the model parameters. Application of the developed model to Sn–15 wt-%Pb slurries has revealed a number of microstructural and rheological characteristics of SSM slurries. Under shear flow, the steady state represents the dynamic equilibrium between two opposite processes, agglomeration and deagglomeration. Under steady state, the microstructure of a SSM slurry is characterised by spherical particle morphology, uniform particle size, constant average agglomerate size and constant effective solid fraction. The theoretical analysis shows that there is an strong coupling between the microstructure and the steady state viscosity. Shear rate affects viscosity of SSM slurries by changing the amount of entrapped liquid between solid ...
Hongchao Luo - One of the best experts on this subject based on the ideXlab platform.
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Rheological Behavior of Semisolid Al-6.5wt%Si Alloy under Cyclic Shear Deformation
2016Co-Authors: Hongchao Luo, Junmei Yang, Liyuan SunAbstract:Abstract. In the present work, the MCF model for Semisolid Metal slurries (SSMS) is applied to investigate the thixotropy of the Al-6.5wt%Si alloy under cyclic shear deformation. The study shows that the Semisolid Al-6.5wt%Si alloy has the behavior of thixotropy. The area of the hysteresis loop increases with decreasing the up-time, the initial shear rate and increasing resting time, solid volume fraction and maximum shear rate, respectively. These results have qualitative agreement with the experimental data. The origin of the hysteresis loop is atrributed to the difference between the deagglomeration rate and the agglomeration rate
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Rheological Behavior of Semisolid Al-6.5wt%Si Alloy at Transient State
2016Co-Authors: Hongchao Luo, Wei WangAbstract:Abstract. In the present work, the rheological model for Semisolid Metal slurries (SSMS) is constructed and then applied to the Al-6.5wt%Si alloy to investigate its rheological behavior at transient state during isothermal shearing and isothermal resting. Firstly, the present study shows that the agreement of the variation of viscosity and the average agglomerate size with shearing time and resting time shows that the microstructure of SSMS determines its rheological behavior. Secondly, the deagglomeration of particles is about two orders of magnitude faster than agglomeration, which is in agreement with the experimental measurement. Finally, the Al-6.5wt%Si alloy at transient state has the behavior of “shear-thinning”, but not “shear-thickening ” predicted in the documents
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the steady state rheological behavior of Semisolid alsi6mg2 alloy
Advanced Materials Research, 2011Co-Authors: Hongchao Luo, Shi Pu Chen, Qin NieAbstract:In the present work, basing on the rheological model of Chen and Fan (CF) [1] of Semisolid Metal slurries (SSMS), the rheological behavior at steady state of AlSi6Mg2 alloy is investigated. Experimental results on steady state viscosity of the present system in the literature are used to determine the parameters of the CF model by fitting. It has been shown that the steady state viscosity and the average agglomerate size increase with increasing the solid volume fraction and decreasing the shear rate. The theoretical prediction of the CF model is in good agreement with the experimental results in the literatures quantitatively. The importance of the effective solid volume fraction is shown by explaining the strong coupling between the viscosity and the microstructure. Specifically, the external flow conditions such as shear rate influences the viscosity by changing the agglomeration degree of the solid particles, that is, the effective solid volume fraction and then changing the viscosity.
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rheological behavior of Semisolid al 6 5wt si alloy at transient state
Advanced Materials Research, 2011Co-Authors: Hongchao Luo, Wei WangAbstract:In the present work, the rheological model for Semisolid Metal slurries (SSMS) is constructed and then applied to the Al-6.5wt%Si alloy to investigate its rheological behavior at transient state during isothermal shearing and isothermal resting. Firstly, the present study shows that the agreement of the variation of viscosity and the average agglomerate size with shearing time and resting time shows that the microstructure of SSMS determines its rheological behavior. Secondly, the deagglomeration of particles is about two orders of magnitude faster than agglomeration, which is in agreement with the experimental measurement. Finally, the Al-6.5wt%Si alloy at transient state has the behavior of “shear-thinning”, but not “shear-thickening” predicted in the documents.
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a steady state model for the rheological behavior of Semisolid al 6 5wt si alloy
Advanced Materials Research, 2011Co-Authors: Hongchao Luo, Wei WangAbstract:In the present work, The Chen and Fan (CF) model [1] of Semisolid Metal slurries (SSMS) is improved by modifying the expression of the packing parameter, of the solid particles and then the modified CF (MCF) model is obtained. Subsequently, the MCF model is applied to the Al-6.5wt%Si alloy to investigate its rheological behavior at steady state. The factors which affect the steady state behavior have been studied. It has been shown that the steady state viscosity and the average agglomerate size increase with increasing the solid volume fraction and decreasing the shear rate. The prediction of the model is in good agreement with the experimental results in the literatures qualitatively. The importance of the effective solid volume fraction is shown by explaining the strong coupling between the viscosity and the microstructure. The external flow conditions such as shear rate etc change the agglomeration degree, that is, the effective solid volume fraction and then the viscosity
Wei Wang - One of the best experts on this subject based on the ideXlab platform.
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Rheological Behavior of Semisolid Al-6.5wt%Si Alloy at Transient State
2016Co-Authors: Hongchao Luo, Wei WangAbstract:Abstract. In the present work, the rheological model for Semisolid Metal slurries (SSMS) is constructed and then applied to the Al-6.5wt%Si alloy to investigate its rheological behavior at transient state during isothermal shearing and isothermal resting. Firstly, the present study shows that the agreement of the variation of viscosity and the average agglomerate size with shearing time and resting time shows that the microstructure of SSMS determines its rheological behavior. Secondly, the deagglomeration of particles is about two orders of magnitude faster than agglomeration, which is in agreement with the experimental measurement. Finally, the Al-6.5wt%Si alloy at transient state has the behavior of “shear-thinning”, but not “shear-thickening ” predicted in the documents
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rheological behavior of Semisolid al 6 5wt si alloy at transient state
Advanced Materials Research, 2011Co-Authors: Hongchao Luo, Wei WangAbstract:In the present work, the rheological model for Semisolid Metal slurries (SSMS) is constructed and then applied to the Al-6.5wt%Si alloy to investigate its rheological behavior at transient state during isothermal shearing and isothermal resting. Firstly, the present study shows that the agreement of the variation of viscosity and the average agglomerate size with shearing time and resting time shows that the microstructure of SSMS determines its rheological behavior. Secondly, the deagglomeration of particles is about two orders of magnitude faster than agglomeration, which is in agreement with the experimental measurement. Finally, the Al-6.5wt%Si alloy at transient state has the behavior of “shear-thinning”, but not “shear-thickening” predicted in the documents.
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a steady state model for the rheological behavior of Semisolid al 6 5wt si alloy
Advanced Materials Research, 2011Co-Authors: Hongchao Luo, Wei WangAbstract:In the present work, The Chen and Fan (CF) model [1] of Semisolid Metal slurries (SSMS) is improved by modifying the expression of the packing parameter, of the solid particles and then the modified CF (MCF) model is obtained. Subsequently, the MCF model is applied to the Al-6.5wt%Si alloy to investigate its rheological behavior at steady state. The factors which affect the steady state behavior have been studied. It has been shown that the steady state viscosity and the average agglomerate size increase with increasing the solid volume fraction and decreasing the shear rate. The prediction of the model is in good agreement with the experimental results in the literatures qualitatively. The importance of the effective solid volume fraction is shown by explaining the strong coupling between the viscosity and the microstructure. The external flow conditions such as shear rate etc change the agglomeration degree, that is, the effective solid volume fraction and then the viscosity
J Y Chen - One of the best experts on this subject based on the ideXlab platform.
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modelling of rheological behaviour of Semisolid Metal slurries part 1 theory
Materials Science and Technology, 2002Co-Authors: J Y Chen, Z. FanAbstract:AbstractIn this paper, part of a series, a microstructural model is presented which describes the rheological behaviour of liquid-like Semisolid Metal (SSM) slurries under a simple shearing flow. A liquid-like SSM slurry is considered as a suspension in which interacting spherical solid particles of low cohesion are dispersed in a liquid matrix. In a simple shear flow field, the dynamic interactions between solid particles result in the formation of agglomerates. Under viscous forces, collisions between agglomerates lead to the formation of new agglomerates of a larger size, and at the same time agglomerates also break up giving rise to agglomerates of a smaller size. At a particular time, the state of agglomeration is described by a structural parameter n, which is defined as the average number of particles in the agglomerates. It is believed that it is the state of agglomeration which determines the rheological properties of SSM slurries, whereas the external flow conditions, such as shear rate and shea...
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modelling of rheological behaviour of Semisolid Metal slurries part 2 steady state behaviour
Materials Science and Technology, 2002Co-Authors: Z. Fan, J Y ChenAbstract:AbstractIn this part of the current series, the rheological model presented in Part 1 is applied to study the steady state behaviour of Semisolid Metal (SSM) slurries. Experimental results on the steady state viscosity of Sn–15 wt-%Pb slurries in the literature are used to determine the model parameters. Application of the developed model to Sn–15 wt-%Pb slurries has revealed a number of microstructural and rheological characteristics of SSM slurries. Under shear flow, the steady state represents the dynamic equilibrium between two opposite processes, agglomeration and deagglomeration. Under steady state, the microstructure of a SSM slurry is characterised by spherical particle morphology, uniform particle size, constant average agglomerate size and constant effective solid fraction. The theoretical analysis shows that there is an strong coupling between the microstructure and the steady state viscosity. Shear rate affects viscosity of SSM slurries by changing the amount of entrapped liquid between solid ...
Kamel Fezzaa - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound
Acta Materialia, 2018Co-Authors: Bing Wang, Dongyue Tan, Tung Lik Lee, Jia Chuan Khong, Thomas Connolley, Feng Wang, Kamel FezzaaAbstract:Ultrasound processing of Metal alloys is an environmental friendly and promising green technology for liquid Metal degassing and microstructural refinement. However many fundamental issues in this field are still not fully understood, because of the difficulties in direct observation of the dynamic behaviours caused by ultrasound inside liquid Metal and Semisolid Metals during the solidification processes. In this paper, we report a systematic study using the ultrafast synchrotron X-ray imaging (up to 271,554 frame per second) technique available at the Advanced Photon Source, USA and Diamond Light Source, UK to investigate the dynamic interactions between the ultrasonic bubbles/acoustic flow and the solidifying phases in a Bi-8%Zn alloy. The experimental results were complimented by numerical modelling. The chaotic bubble implosion and dynamic bubble oscillations were revealed in-situ for the first time in liquid Metal and Semisolid Metal. The fragmentation of the solidifying Zn phases and breaking up of the liquid-solid interface by ultrasonic bubbles and enhanced acoustic flow were clearly demonstrated and agreed very well with the theoretical calculations. The research provides unambiguous experimental evidence and robust theoretical interpretation in elucidating the dominant mechanisms of microstructure fragmentation and refinement in solidification under ultrasound.
