Investigation on microstructural patterns and hot crack in the molten pool via integrated finite-element and phase-field modeling

A multi-scale model combing phase-field model and finite-element model is applied to study microstructural patterns and susceptibility of hot crack in the molten pool. Firstly, the macroscopic temperature field during welding is calculated by finite-element model, and the geometry, thermal gradient G and solidification rate R are obtained. Then these macroscopic calculation results are employed as inputs to phase-field model. Finally, morphologies of microstructural patterns and susceptibility of hot crack at different locations in the molten pool are studied. Predicted and experimental morphologies of microstructural patterns are dendritic. Predicted primary dendrite arm spacing decreases from the bottom to the top surface in the molten pool, which agrees well with experimental measurements. The formation of hot crack is related to dendritic growth and micro-segregation between dendrites. Predicted susceptibility of hot crack decreases from the bottom to the top surface in the molten pool.