The effect of convective flow on a spherical crystal growth in the undercooled melt with a moderate far field flow is studied. The asymptotic solution of the evolution of the interface of the spherical crystal growth ...The effect of convective flow on a spherical crystal growth in the undercooled melt with a moderate far field flow is studied. The asymptotic solution of the evolution of the interface of the spherical crystal growth is obtained by the matched asymptotic expansion method. The analytic result shows that the convective flow in the undercooled melt has a strong effect on the evolution of spherical crystal growth. The convective flow induced by the far field flow makes the interface of the growing spherical crystal enhance its growth velocity in the upstream direction of the far field flow and inhibit growth in the downstream direction, and the interface of the decaying spherical crystal further decay in the upstream direction and inhibit decay in the downstream direction. The maximum growth velocity of the interface of the spherical crystal influenced by the far field flow is obtained.展开更多
On the base of nonlinear liquidus and solidus,an extended model for dendrite growth in bulk undercooled melts was developed under local non-equilibrium conditions both at the interface and in the bulk liquid.In terms ...On the base of nonlinear liquidus and solidus,an extended model for dendrite growth in bulk undercooled melts was developed under local non-equilibrium conditions both at the interface and in the bulk liquid.In terms of thermodynamic calculations of the phase diagram,the model predictions are relatively realistic physically,since few fitting parameters are used in the model predictions.Adopting three characteristic velocities,i.e.the critical velocity of absolute solute stability(VC*),the velocity of maximal tip radius(VRm),and the velocity of bulk liquid diffusion(VD),a quantitative agreement is obtained between the model predictions and the experimental results in undercooled Ni-0.7%B and Ni-1%Zr(molar fraction) alloys,and the overall solidification process can be categorized.展开更多
基金the National Basic Research Program of China (the Project 973) (2006CB605205)the National Natural Science Foundation of China (10672019)
文摘The effect of convective flow on a spherical crystal growth in the undercooled melt with a moderate far field flow is studied. The asymptotic solution of the evolution of the interface of the spherical crystal growth is obtained by the matched asymptotic expansion method. The analytic result shows that the convective flow in the undercooled melt has a strong effect on the evolution of spherical crystal growth. The convective flow induced by the far field flow makes the interface of the growing spherical crystal enhance its growth velocity in the upstream direction of the far field flow and inhibit growth in the downstream direction, and the interface of the decaying spherical crystal further decay in the upstream direction and inhibit decay in the downstream direction. The maximum growth velocity of the interface of the spherical crystal influenced by the far field flow is obtained.
基金Projects(50501020, 50395103, 50431030) supported by the National Natural Science Foundation of ChinaProject(NCET-05-870) supported by Program for New Century Excellent Talents in Chinese UniversityProject(CX200706) supported by the Doctorate Foundation of Northwestern Polytechnical University,China
文摘On the base of nonlinear liquidus and solidus,an extended model for dendrite growth in bulk undercooled melts was developed under local non-equilibrium conditions both at the interface and in the bulk liquid.In terms of thermodynamic calculations of the phase diagram,the model predictions are relatively realistic physically,since few fitting parameters are used in the model predictions.Adopting three characteristic velocities,i.e.the critical velocity of absolute solute stability(VC*),the velocity of maximal tip radius(VRm),and the velocity of bulk liquid diffusion(VD),a quantitative agreement is obtained between the model predictions and the experimental results in undercooled Ni-0.7%B and Ni-1%Zr(molar fraction) alloys,and the overall solidification process can be categorized.
