Narrow Results

In the paper, the grain growth of TC4-DT (Damage Tolerance) alloy joint during electron beam welding (EBW) process was simulated by using Cellular Automaton method. In order to consider the effects of the growth of neighborhood cellular on the center cells in the model, the solid fraction and solute distribution algorithms of classical CA model were improved. The growth of equiaxed grains and columnar crystals under uniform and nonuniform temperature fields was simulated successfully by applying the modified model, respectively. The temperature distribution near the fusion line of TC4-DT EBW joint was also calculated by using double ellipsoid heat source model. Then, coupling the CA model with the temperature field, the grain growth process of the cross-section of the welded zone was simulated. The simulation result fits well with experimental ones on the morphology and the size of the columnar crystals.

Laser Powder Bed Fusion (LPBF) is an additive manufacturing method that manufactures high density and quality metal products. We present a coupled grain growth and heat transfer modeling technique to understand the materials microstructure evolution in metals during the cooling process of LPBF. The phase-field model is combined with a transient heat transfer equation to simulate the solidification and crystallization of the melt pool simultaneously. Specifically, the variable domain and driving force of the order parameters in the phase-field calculation are defined using current temperature distribution. Additionally, the latent heat generated by crystallization is introduced as a heat source to affect temperature evolution in the cooling process. The finite element method with a staggering strategy is employed to solve the coupled governing equations on an irregular computational domain. The computational framework is verified in a one-dimensional solidification problem by comparing the velocity of the fluid-solid interface. The two-way coupling solution of solidification and crystallization is studied in an example of LPBF of Aluminum alloys.