Prediction of Thermal Residual Stress and Microstructure in Direct Laser Metal Deposition via a Coupled Finite Element and Multiphase Field Framework

Direct laser metal deposition (DLMD) is a modern powder-fed additive manufacturing process, which builds up complex objects layer by layer, providing a potential capacity to produce key structural components specifically for the aerospace industry. The printing process is of a multidisciplinary nature, and has gained increasing attention in the areas of engineering mechanics, material science, control engineering and many other related fields. The quality control of the printed part depends on a large number of process parameters. The aim of this work, therefore, is to develop a coupled finite element and multiphase field framework, that provides an effective way to understand the quantitative relationship between the process parameters, temperature history, thermally-induced residual stresses and microstructures in the DLMD process. More specifically, the established multiscale framework is able to sequentially couple the heat transfer, metal melting/solidification, and stress analysis to simulate the macroscopic temperature distribution, thermal residual stresses and dendrite growth and solute segregation in a thin wall structure made of a binary nickel-copper alloy. The latest simulation technologies are used to model the process of progressive material deposition as well as the movement of the laser beam. It has been found that the high intensity laser introduced in DLMD can produce a complex thermal history and a significant level of thermal residual stresses and distortion. Microstructure predictions demonstrate the location-dependent morphology evolution, e.g., the dendrite spacing and the degree of solute segregation, attributed to the spatially variant temperature history.