scholarly journals The Interaction between Grains during Columnar-to-Equiaxed Transition in Laser Welding: A Phase-Field Study

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1647
Author(s):  
Lingda Xiong ◽  
Chunming Wang ◽  
Zhimin Wang ◽  
Ping Jiang
Keyword(s):  
Laser Welding ◽  
Phase Field ◽  
Numerical Results ◽  
Model Alloy ◽  
Columnar Dendrite ◽  
Nucleation Density ◽  
Al Alloy ◽  
Nucleation Undercooling ◽  
Columnar To Equiaxed Transition ◽  
Equiaxed Grains

A phase-field model was applied to study CET (columnar-to-equiaxed transition) during laser welding of an Al-Cu model alloy. A parametric study was performed to investigate the effects of nucleation undercooling for the equiaxed grains, nucleation density and location of the first nucleation seed ahead of the columnar front on the microstructure of the fusion zone. The numerical results indicated that nucleation undercooling significantly influenced the occurrence and the time of CET. Nucleation density affected the occurrence of CET and the size of equiaxed grains. The dendrite growth behavior was analyzed to reveal the mechanism of the CET. The interactions between different grains were studied. Once the seeds ahead of the columnar dendrites nucleated and grew, the columnar dendrite tip velocity began to fluctuate around a value. It did not decrease until the columnar dendrite got rather close to the equiaxed grains. The undercooling and solute segregation profile evolutions of the columnar dendrite tip with the CET and without the CET had no significant difference before the CET occurred. Mechanical blocking was the major blocking mechanism for the CET. The equiaxed grains formed first were larger than the equiaxed grains formed later due to the decreasing of undercooling. The size of equiaxed grain decreased from fusion line to center line. The numerical results were basically consistent with the experimental results obtained by laser welding of a 2A12 Al-alloy.

Numerical and Experimental Investigation of NH4Cl Solidification

2010 ◽  
Vol 649 ◽  
pp. 367-372 ◽  
Author(s):  
Laszlo Könözsy ◽  
Mihaela Stefan Kharicha ◽  
Sven Eck ◽  
Meng Huai Wu ◽  
Andreas Ludwig
Keyword(s):  
Optical Measurement ◽  
Model Alloy ◽  
Columnar Dendrite ◽  
Solidification Model ◽  
Benchmark Experiment ◽  
Diffusion Controlled ◽  
Image Velocimetry ◽  
Model Equations ◽  
Volume Method ◽  
Equiaxed Grains

This paper deals with the validation of a volume averaged multiphase solidification model based on a benchmark experiment using NH4Cl-H2O as model alloy and Particle Image Velocimetry (PIV) as optical measurement method. For the numerical modelling of the solidification, different phases (e.g. liquid, equiaxed grains and columnar dendrite trunks) have been considered. The mass, momentum, energy conservation and species transport equations for each phase have been solved. The Eulerian-Eulerian model equations have been implemented in the commercial Finite Volume Method based software FLUENT-ANSYS v6.3 using User-Defined Functions (UDF). The mass transfer has been modelled by diffusion controlled crystal growth. The simulation of the NH4Cl-H2O solidification has been numerically investigated as a two-dimensional unsteady process in the cross-section of a 100 x 80 x 10 (mm3) experimental benchmark. Since during the experiment both columnar and equiaxed growth of NH4Cl have been observed, both phenomena have been considered in the simulation. The predicted distribution of the solidification front and the measured thickness of the mushy zone have been compared with the measurements.

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.

scholarly journals Modelling of Microstructure Evolution during Laser Processing of Intermetallic Containing Ni-Al Alloys

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1051
Author(s):  
Mohammad Amin Jabbareh ◽  
Hamid Assadi
Keyword(s):  
Additive Manufacturing ◽  
Rapid Solidification ◽  
Microstructure Evolution ◽  
Phase Field ◽  
Laser Processing ◽  
Field Model ◽  
Phase Field Model ◽  
Intermetallic Phases ◽  
Al Alloy ◽  
Kinetic Effects

There is a growing interest in laser melting processes, e.g., for metal additive manufacturing. Modelling and numerical simulation can help to understand and control microstructure evolution in these processes. However, standard methods of microstructure simulation are generally not suited to model the kinetic effects associated with rapid solidification in laser processing, especially for material systems that contain intermetallic phases. In this paper, we present and employ a tailored phase-field model to demonstrate unique features of microstructure evolution in such systems. Initially, the problem of anomalous partitioning during rapid solidification of intermetallics is revisited using the tailored phase-field model, and the model predictions are assessed against the existing experimental data for the B2 phase in the Ni-Al binary system. The model is subsequently combined with a Potts model of grain growth to simulate laser processing of polycrystalline alloys containing intermetallic phases. Examples of simulations are presented for laser processing of a nickel-rich Ni-Al alloy, to demonstrate the application of the method in studying the effect of processing conditions on various microstructural features, such as distribution of intermetallic phases in the melt pool and the heat-affected zone. The computational framework used in this study is envisaged to provide additional insight into the evolution of microstructure in laser processing of industrially relevant materials, e.g., in laser welding or additive manufacturing of Ni-based superalloys.

Multi-component phase-field simulation of microstructural evolution and elemental distribution in Fe–Cu–Mn–Ni–Al alloy

Calphad ◽  
2020 ◽  
Vol 69 ◽  
pp. 101759
Author(s):  
Yuanyang Sun ◽  
Yuhong Zhao ◽  
Baojun Zhao ◽  
Zhen Guo ◽  
Xiaolin Tian ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Phase Field ◽  
Al Alloy ◽  
Elemental Distribution ◽  
Phase Field Simulation ◽  
Field Simulation ◽  
Component Phase
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