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G. Liu - One of the best experts on this subject based on the ideXlab platform.
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Solidification behaviour under intensive Forced Convection
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Zhongyun Fan, G. Liu, M. HitchcockAbstract:Abstract Solidification behaviour of AZ91D Mg-alloy and 357 Al-alloy under intensive Forced Convection in the rheo-die-casting process, was investigated experimentally to understand the effects of the intensity of Forced Convection and shearing time on the nucleation and growth behaviour. It was found that under intensive Forced Convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt. All the nuclei could survive due to the uniform temperature and composition fields created by the Forced Convection. This has been named as ‘effective and continuous nucleation’. It is also found that the nuclei grow spherically with an extremely fast growth rate. This makes the primary solidification essentially a slow coarsening process, in which Ostwald ripening takes place by dissolution of the smaller particles. In addition, it was found that intensive Forced Convection partially suppresses the formation of the primary phase during the primary solidification, and that this effect is more pronounced in 357 Al-alloy than in AZ91D Mg-alloy.
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solidification behaviour of az91d alloy under intensive Forced Convection in the rdc process
Acta Materialia, 2005Co-Authors: Zhongyun Fan, G. LiuAbstract:Rheo-diecasting (RDC) is a new semisolid processing technology for production of near net shape components. In this work, the solidification behaviour of AZ91D alloy under intensive Forced Convection in the RDC process was investigated experimentally to understand the effects of the intensity of Forced Convection, shearing time and shearing temperature on the nucleation and growth behaviour. It was found that under intensive Forced Convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt. All the nuclei could survive due to the uniform temperature and composition fields created by the Forced Convection. This has been named as continuous effective nucleation. It is also found that the nuclei grow spherically with an extremely fast growth rate. This makes the primary solidification essentially a coarsening process, in which Ostwald ripening takes place by dissolution of the smaller particles. Secondary solidification of the intensively sheared semisolid slurry takes place also through effective nucleation, but with dendritic growth. Increasing the intensity of Forced Convection enhances nucleation and promotes the formation of the primary phase during the secondary solidification in the shot sleeve. The final solidification microstructure is strongly dependent on the presence of turbulence rather than the shear rate.
Zhongyun Fan - One of the best experts on this subject based on the ideXlab platform.
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Solidification Behaviour of 357 Al-Alloy under Intensive Forced Convection
Materials Science Forum, 2006Co-Authors: M. Hitchcock, Zhongyun FanAbstract:Solidification behaviour of 357 Al-alloy under intensive Forced Convection in the rheo-die-casting (RDC) process, was investigated experimentally to understand the effects of the intensity of Forced Convection and shearing time on the nucleation and growth behaviour. It was found that under intensive Forced Convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt. All the nuclei could survive due to the uniform temperature and composition fields created by the Forced Convection. This has been named as ‘effective and continuous nucleation’. It is also found that the nuclei grow spherically with an extremely fast growth rate. This makes the primary solidification essentially a slow coarsening process, in which Ostwald ripening takes place by dissolution of the smaller particles. In addition, it was found that intensive Forced Convection suppresses partially the formation of the primary phase, promote nucleation of the primary particles, and hinders the particle growth.
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Solidification behaviour under intensive Forced Convection
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Zhongyun Fan, G. Liu, M. HitchcockAbstract:Abstract Solidification behaviour of AZ91D Mg-alloy and 357 Al-alloy under intensive Forced Convection in the rheo-die-casting process, was investigated experimentally to understand the effects of the intensity of Forced Convection and shearing time on the nucleation and growth behaviour. It was found that under intensive Forced Convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt. All the nuclei could survive due to the uniform temperature and composition fields created by the Forced Convection. This has been named as ‘effective and continuous nucleation’. It is also found that the nuclei grow spherically with an extremely fast growth rate. This makes the primary solidification essentially a slow coarsening process, in which Ostwald ripening takes place by dissolution of the smaller particles. In addition, it was found that intensive Forced Convection partially suppresses the formation of the primary phase during the primary solidification, and that this effect is more pronounced in 357 Al-alloy than in AZ91D Mg-alloy.
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solidification behaviour of az91d alloy under intensive Forced Convection in the rdc process
Acta Materialia, 2005Co-Authors: Zhongyun Fan, G. LiuAbstract:Rheo-diecasting (RDC) is a new semisolid processing technology for production of near net shape components. In this work, the solidification behaviour of AZ91D alloy under intensive Forced Convection in the RDC process was investigated experimentally to understand the effects of the intensity of Forced Convection, shearing time and shearing temperature on the nucleation and growth behaviour. It was found that under intensive Forced Convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt. All the nuclei could survive due to the uniform temperature and composition fields created by the Forced Convection. This has been named as continuous effective nucleation. It is also found that the nuclei grow spherically with an extremely fast growth rate. This makes the primary solidification essentially a coarsening process, in which Ostwald ripening takes place by dissolution of the smaller particles. Secondary solidification of the intensively sheared semisolid slurry takes place also through effective nucleation, but with dendritic growth. Increasing the intensity of Forced Convection enhances nucleation and promotes the formation of the primary phase during the secondary solidification in the shot sleeve. The final solidification microstructure is strongly dependent on the presence of turbulence rather than the shear rate.
Michitsugu Mori - One of the best experts on this subject based on the ideXlab platform.
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photographic study of bubble behaviors in Forced Convection subcooled boiling
International Journal of Heat and Mass Transfer, 2004Co-Authors: Rong Situ, Ye Mi, Mamoru Ishii, Michitsugu MoriAbstract:Forced Convection subcooled water boiling experiments were conducted in a vertical annular channel. A high-speed digital video camera was applied to record the dynamics of the subcooled boiling process. The flow visualization results show that the bubble departure frequency generally increases as the heat flux increases. For some cases, the departure frequency may reach a limit around 1000 bubbles/s. In addition, bubble lift-off diameter, bubble growth rate and bubble velocity after bubble lift-off were determined by analyzing the images. The experimental data obtained from this study can be used in modeling the bubble departure frequency, bubble lift-off diameter, and bubble dynamics in Forced Convection subcooled boiling.
M. Hitchcock - One of the best experts on this subject based on the ideXlab platform.
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Solidification Behaviour of 357 Al-Alloy under Intensive Forced Convection
Materials Science Forum, 2006Co-Authors: M. Hitchcock, Zhongyun FanAbstract:Solidification behaviour of 357 Al-alloy under intensive Forced Convection in the rheo-die-casting (RDC) process, was investigated experimentally to understand the effects of the intensity of Forced Convection and shearing time on the nucleation and growth behaviour. It was found that under intensive Forced Convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt. All the nuclei could survive due to the uniform temperature and composition fields created by the Forced Convection. This has been named as ‘effective and continuous nucleation’. It is also found that the nuclei grow spherically with an extremely fast growth rate. This makes the primary solidification essentially a slow coarsening process, in which Ostwald ripening takes place by dissolution of the smaller particles. In addition, it was found that intensive Forced Convection suppresses partially the formation of the primary phase, promote nucleation of the primary particles, and hinders the particle growth.
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Solidification behaviour under intensive Forced Convection
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Zhongyun Fan, G. Liu, M. HitchcockAbstract:Abstract Solidification behaviour of AZ91D Mg-alloy and 357 Al-alloy under intensive Forced Convection in the rheo-die-casting process, was investigated experimentally to understand the effects of the intensity of Forced Convection and shearing time on the nucleation and growth behaviour. It was found that under intensive Forced Convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt. All the nuclei could survive due to the uniform temperature and composition fields created by the Forced Convection. This has been named as ‘effective and continuous nucleation’. It is also found that the nuclei grow spherically with an extremely fast growth rate. This makes the primary solidification essentially a slow coarsening process, in which Ostwald ripening takes place by dissolution of the smaller particles. In addition, it was found that intensive Forced Convection partially suppresses the formation of the primary phase during the primary solidification, and that this effect is more pronounced in 357 Al-alloy than in AZ91D Mg-alloy.
Hideo Kimoto - One of the best experts on this subject based on the ideXlab platform.
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Forced Convection heat transfer from a heated circular cylinder with arbitrary surface temperature distributions
Heat Transfer Research, 1999Co-Authors: Kazunari Momose, Hideo KimotoAbstract:A Fredholm-type boundary integral expression for evaluation of the Forced Convection heat transfer from an object with arbitrary surface temperature distributions is proposed. The Fredholm kernel function for a heated circular cylinder was calculated by numerical simulation of the Forced Convection fields, and then generalized heat transfer coefficients for arbitrary surface temperature distributions were defined. By use of the generalized heat transfer coefficients, it is shown that the difference in local heat transfer characteristics between the case of an isothermal cylinder and that of a uniform heat flux one can be interpreted only as the difference of the surface temperature distributions. Moreover, the mechanism of the effect of the surface temperature distribution on the characteristics of Forced Convection heat transfer from a cylinder is clarified in detail through the generalized heat transfer coefficients. © 1999 Scripta Technica, Heat Trans Asian Res, 28(6): 484–499, 1999
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Forced Convection Heat Transfer from a Heated Circular Cylinder with Arbitrary Surface Temperature Distributions.
Transactions of the Japan Society of Mechanical Engineers. B, 1997Co-Authors: Kazunari Momose, Hideo KimotoAbstract:A Fredholm-type boundary integral expression for evaluation of the Forced Convection heat transfer from an object with arbitrary surface temperature distributions is proposed. The Fredholm kernel function for a heated circular cylinder was calculated by numerical simulation of the Forced Convection fields, and then generalized heat transfer coefficients for arbitrary surface temperature distributions were defined. By use of the generalized heat transfer coefficients, it is shown that the difference in local heat transfer characteristics between the case of an isothermal cylinder and that of a uniform heat flux one can be explained only as the difference of the surface temperature distributions. Moreover, the mechanism of the effect of the surface temperature distribution on the characteristics of Forced Convection heat transfer from a cylinder is clarified in detail through the generalized heat transfer coefficients.