Combined finite element and phase field method for simulation of austenite grain growth in the heat-affected zone of a martensitic steel weld

Engineering components operating at high temperature often fail due to the initiation and growth of cracks in the heat-affected zone (HAZ) adjacent to a weld. Understanding the effects of microstructural evolution in the HAZ is important in order to predict and control the final properties of welded joints. This study presents a combined finite-element (FE) and phase-field (PF) method for simulation of austenite grain growth in the HAZ of a tempered martensite (P91) steel weld. The FE method is used to determine the thermal history of the HAZ during gas tungsten arc welding (GTAW) of a P91 steel plate. Then, the calculated thermal history is included in a PF model to simulate grain growth at various positions in the HAZ. The predicted mean grain size and grain distribution match well with experimental data for simulated welds from the literature. The work lays the foundation for optimising the process parameters in welding of P91 and other ferritic/martensitic steels in order to control the final HAZ microstructure.