Browsing by Subject "phase field"

Now showing 1 - 3 of 3
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    Phase field simulation of dendritic microstructure in additively manufactured titanium alloy
    (Elsevier, 2019-01) Zhang, Jing; Wu, Linmin; Zhang, Yi; Meng, Lingbin; Mechanical and Energy Engineering, School of Engineering and Technology
    Additive manufacturing (AM) processes for metals, such as selective laser sintering and electron beam melting, involve rapid solidification process. The microstructure of the fabricated material and its properties strongly depend on the solidification. Therefore, in order to control and optimize the AM process, it is important to understand the microstructure evolution. In this work, using Ti-6Al-4V as a model system, the phase field method is applied to simulate the microstructure evolution in additively manufactured metals. First, the fundamental governing equations are presented. Then the effects of various processing related parameters, including local temperature gradient, scan speed and cooling rate, on dendrites’ morphology and growth velocity are studied. The simulated results show that the dendritic arms grow along the direction of the heat flow. Higher temperature gradient, scan speed and cooling rate will result in small dendritic arm spacing and higher growth velocity. The simulated dendritic morphology and arm spacings are in good agreement with experimental data and theoretical predictions.
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    Phase Field Simulation of Dendritic Solidification of Ti-6Al-4V During Additive Manufacturing Process
    (Springer, 2018-10) Wu, Linmin; Zhang, Jing; Mechanical and Energy Engineering, School of Engineering and Technology
    In this study, the phase field method is applied to simulate the phase transformation of Ti-6Al-4V from liquid phase to solid phase during solidification. The simulated results show the dendritic arms grow along the direction of the heat flow. Droplets are found formed inside the dendrites. Solute enriches in the liquid near the dendritic tips and between the dendritic arms. The effects of various processing parameters, including local temperature gradient, scan speed, and cooling rate, on dendrites morphology and growth velocity are studied. The results show that the higher temperature gradient, scan speed, and cooling rate will result in smaller dendritic arm spacing and higher growth velocity. The simulated dendritic morphology and arm spacings are in good agreement with experimental data and theoretical predictions.
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    Phase-field-lattice Boltzmann method for dendritic growth with melt flow and thermosolutal convection–diffusion
    (Elsevier, 2021-11) Wang, Nanqiao; Korba, David; Liu, Zixiang; Prabhu, Raj; Priddy, Matthew; Yang, Shengfeng; Chen, Lei; Li, Like; Mechanical and Energy Engineering, School of Engineering and Technology
    We propose a new phase-field model formulated within the system of lattice Boltzmann (LB) equation for simulating solidification and dendritic growth with fully coupled melt flow and thermosolutal convection–diffusion. With the evolution of the phase field and the transport phenomena all modeled and integrated within the same LB framework, this method preserves and combines the intrinsic advantages of the phase-field method (PFM) and the lattice Boltzmann method (LBM). Particularly, the present PFM/LBM model has several improved features compared to the existing phase-field models including: (1) a novel multiple-relaxation-time (MRT) LB scheme for the phase-field evolution is proposed to effectively model solidification coupled with melt flow and thermosolutal convection–diffusion with improved numerical stability and accuracy, (2) convenient diffuse interface treatments are implemented for the melt flow and thermosolutal transport which can be applied to the entire domain without tracking the interface, and (3) the evolution of the phase field, flow, concentration, and temperature fields on the level of microscopic distribution functions in the LB schemes is decoupled with a multiple-time-scaling strategy (despite their full physical coupling), thus solidification at high Lewis numbers (ratios of the liquid thermal to solutal diffusivities) can be conveniently modeled. The applicability and accuracy of the present PFM/LBM model are verified with four numerical tests including isothermal, iso-solutal and thermosolutal convection–diffusion problems, where excellent agreement in terms of phase-field and thermosolutal distributions and dendritic tip growth velocity and radius with those reported in the literature is demonstrated. The proposed PFM/LBM model can be an attractive and powerful tool for large-scale dendritic growth simulations given the high scalability of the LBM.