Solidification of a quaternary X5CrNi18-10 alloy during laser beam welding using CALPHAD data in a phase-field approach

Dendritic growth is a common phenomenon during the solidification of alloys, and it has a significant impact on the final microstructure and mechanical properties of the material. This research study investigates the solidification behaviour of quaternary X5CrNi18-10 alloys at thermochemical conditions similar to the laser beam welding (LBW) process. The aim of this investigation is to gain a comprehensive understanding of microstructure evolution at the microscale and their correlation with the macroscopic welding process conditions. To achieve this, a combined approach using the CALculation of PHAse Diagrams (CALPHAD) database and phase-field simulations is employed. Based on the CALPHAD-derived Gibbs energy functions, phase-field simulations are performed to simulate the solidification with dendritic/cellular morphology. The study focuses on solidification microstructure evolution influenced by process conditions such as thermal gradient and LBW velocity at steady-state conditions. By analysing the solidification microstructure morphology in 2D, valuable insights into the solidification kinetics and the influence of local thermal conditions on dendritic growth are obtained. Furthermore, the micro-segregation behaviour of key alloying elements during solidification in the mushy zone is explored. This study will help to enhance the understanding of dendritic solidification in this welding process, facilitating the optimisation of process parameters for improved mechanical properties. • Computationally efficient fitting of Gibbs energy functions for quaternary alloy • Relationship between dendrite tip velocity and radius validated with theory • Critical role of residual liquid pockets in the inter-dendritic region revealed