Computational Modeling of Columnar to Equiaxed Transition in Alloy Solidification

2012 ◽  
Vol 15 (4) ◽  
pp. 216-229 ◽  
Author(s):  
Wajira U. Mirihanage ◽  
Huijuan Dai ◽  
Hongbiao Dong ◽  
David J. Browne
Keyword(s):  
Computational Modeling ◽  
Alloy Solidification ◽  
Columnar To Equiaxed Transition

An Experimental Investigation Into the Effects of Grain Transport on Columnar to Equiaxed Transition During Dendritic Alloy Solidification

1999 ◽  
Vol 121 (2) ◽  
pp. 430-437 ◽  
Author(s):  
J. W. Gao ◽  
C. Y. Wang
Keyword(s):  
Mushy Zone ◽  
Chloride Solution ◽  
Packed Bed ◽  
Model Alloy ◽  
Alloy Solidification ◽  
Pile Up ◽  
Thermally Driven ◽  
Columnar To Equiaxed Transition ◽  
Vertical Test ◽  
Dendritic Alloy

An experimental study has been conducted to investigate the effects of grain transport on the columnar to equiaxed transition (CET) in dendritic alloy solidification. Using the aqueous ammonium chloride solution as a transparent model alloy, experiments were performed in a vertical test cell with cooling from the top, resulting in unidirectional columnar crystals growing downwards. Ahead of the columnar front, equiaxed nuclei were observed to originate mostly by fragmentation of the columnar dendrites in the presence of a thermally driven flow in the melt beneath the columnar mushy zone. Being heavier than the liquid, these fragments fall into the bulk melt where they may grow or remelt. The survived equiaxed crystals finally settle towards the floor and pile up to form an equiaxed bed. The CET occurs when the bottom equiaxed packed bed rises and eventually obstructs the columnar mushy zone growing from the upper surface. Therefore, the CET in the present configuration was predominantly controlled by the sedimentation of equiaxed crystals. A parametric study by varying initial concentration, cooling rate, and superheat was performed.

scholarly journals Simulation of the Columnar-to-Equiaxed Transition in Alloy Solidification - The Effect of Nucleation Undercooling, Density of Nuclei in Bulk Liquid and Alloy Solidification Range on the Transition

2008 ◽  
Vol 139 ◽  
pp. 129-134 ◽  
Author(s):  
H.J. Dai ◽  
H.B. Dong ◽  
H.V. Atkinson ◽  
Peter D. Lee
Keyword(s):  
Dendritic Structure ◽  
Bulk Liquid ◽  
Structure Evolution ◽  
Alloy Solidification ◽  
Solidification Range ◽  
Nucleation Undercooling ◽  
Grain Structures ◽  
Columnar To Equiaxed Transition ◽  
Equiaxed Grains ◽  
The Relationship

A coupled cellular automaton-finite difference (CA-FD) model is used to simulate the detailed dendritic structure evolution of the columnar-to-equiaxed transition (CET) for Al-Cu alloys during solidification. The effects of material properties (nucleation undercooling, density of nuclei in bulk liquid and alloy solidification range) on the CET are investigated. Simulated results reveal that: (1) equiaxed grains form at an earlier stage with a smaller critical nucleation undercooling; (2) CET is promoted if the density of nuclei in bulk liquid is increased; (3) extending the alloy solidification range promotes the CET. Finally, CET maps corresponding to different alloy concentrations are constructed, illustrating the relationship between processing conditions and the resulting grain structures for alloys with different solidification ranges.

Sign in / Sign up

Export Citation Format

Share Document