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TECHNICAL PAPERS: Melting and Solidification

Solidification Microstructure Evolution Model for Laser Cladding Process

[+] Author and Article Information
Y. Cao

Department of Mechanical and Aerospace Engineering,  University of Missouri-Rolla, Rolla, MO 65409-1060

J. Choi

Department of Mechanical and Aerospace Engineering,  University of Missouri-Rolla, Rolla, MO 65409-1060jchoi@umr.edu

J. Heat Transfer 129(7), 852-863 (Aug 10, 2006) (12 pages) doi:10.1115/1.2712856 History: Received May 01, 2006; Revised August 10, 2006

The laser cladding process inherently includes multiscale, highly nonlinear, and non-equilibrium transport phenomena due to nonuniform and rapid heat flow caused by the laser and the material interaction. In this work, a process model of solidification micro-structure evolution for the laser cladding process has been studied by utilizing a phase-field method. The phase-field method has become a widely used computational tool for the modeling of solidification micro-structure evolution with the advantage of avoiding tracking the interface explicitly and satisfying interfacial boundary conditions. In the present work, the numerical solutions of a phase-field model have been analyzed. The linking of the macroscale process and solidification microstructure evolution was examined by considering the relationship of macro- and micro-parameters. The effects of melt undercooling and anisotropy on the solidification micro-structure have also been studied. The predicted results with different undercoolings were compared with the microsolvability theory and a good agreement was found. Different solidification morphologies of different locations in the melt-pool are also investigated. To quantitatively study the effect of heat flux on the dendritic growth, the dendrite tip analysis was carried out. It was observed that the dendrite tip that grows in the same direction with the heat flux shows a much higher velocity than a tip that grows in the opposite direction of the heat flux.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Scheme of macro∕micro-scale coupling method

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Figure 2

Calculation results of macro-model (powder velocity 0.15m∕s, powder diameter 120μm, laser beam power 1000W, radius of laser beam 0.7mm, powder interval 0.2ms, and laser absorptivity, 0.3)

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Figure 3

Pure metal dendrite growth: (a) interface shape (contour ϕ=0) shown every 5000 iterations; (b) convergence of dimensionless dendrite tip velocity as increasing iteration number (simulation parameters λ=1.5957, Δ=0.65, α=1, Δx=Δy=0.4, δt=0.02, ε4=0.05)

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Figure 4

Calculation Results for alloy solidification with different Lewis numbers (MC∞=0.1, k=0.15, λ=6.3829, D=4.0, Δx=Δy=0.4, ε4=0.05)

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Figure 5

Scheme of cell location

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Figure 6

Temperature history of cell 1, cell 2, and cell 3

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Figure 7

Dendritic growth with heat flux case 1 (cell 1) (MC∞=0.1, k=0.15, D=4.0, λ=6.3829, Le=10, δt=0.0008, Δx=Δy=0.4, ε4=0.05)

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Figure 8

Dendritic growth with heat flux case 2 (cell 2) (MC∞=0.1, k=0.15, D=4.0, λ=6.3829, Le=10, δt=0.0008, Δx=Δy=0.4, ε4=0.05)

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Figure 9

Dendritic growth with heat flux case 3 (cell 3) (MC∞=0.1, k=0.15, D=4.0, λ=6.3829, Le=10, δt=0.0008, Δx=Δy=0.4, ε4=0.05)

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Figure 10

Effect of undercooling (Δ) on dendrite growth pattern (λ=6.3829, α=4.0, Δx=Δy=0.4, δt=0.08, ε4=0.05)

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Figure 11

Dimensionless tip velocity evolution with different undercooling

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Figure 12

Relationship between dimensionless tip velocity and square of undercooling

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