Discussed first is a new Dynamic Kinetic Monte Carlo (KMC) method for predicting grain structures in additively manufactured metals fabricated by laser-based powder bed fusion techniques. The distinguishing technical feature in the Dynamic KMC method is that, unlike existing KMC methods, it updates both the melt pool (MP) and heat affected zone (HAZ) boundaries at every frame of time within the underlying Potts model during grain nucleation and growth. The model thus captures evolution of microstructure due to both intralayer and interlayer heat accumulation during the additive build process. Results are demonstrated for a 6-layer, thin-walled, Inconel 625 structure. Following introduction of the Dynamic KMC microstructure prediction tool, the importance of capturing microstructure and residual stress in additively manufactured metal parts is demonstrated for three post-processing operations, including laser shock peening, laser impact welding, and machining. In the laser shock peening simulations, the inhomogeneous and anisotropic material response due to the Inconel 625 microstructure reveals asymmetric distributions of the resulting residual stress field. In the laser impact welding of aluminum 1100 and stainless steel 316L, it is shown that the microstructure influences the degree of material jetting as well as the peak temperatures observed. In the high-speed end milling of an Inconel 625 directed energy deposition (DED) part, significant influence of the inherent DED residual stress is observed on the machining-induced distortion, and this influence is seen to vary greatly with the machining strategy.
Arif Malik is Associate Professor and Associate Dept. Head of Mechanical Engineering at The University of Texas at Dallas. Prior to joining UT Dallas, Malik was Assistant Professor of Aerospace & Mechanical Engineering at Saint Louis University. He received his PhD from Wright State University, and prior to this he held several positions during 15 years in industry, including 5 years in a start-up company he co-founded to supply process control software for the metals manufacturing industry. Malik is a recipient of the National Science Foundation CAREER Award, and his research involves uncertainty-based and multi-scale computational mechanics to address problems in advanced manufacturing. In 2018, he was invited to serve as Technical Program Chair for the ASME Manufacturing Science and Engineering Conference, hosted by Texas A&M, and he has served as an Associate Editor for the Journal of Manufacturing Processes. In addition to research and teaching, Malik and his graduate students run an annual “Engineering Brighter Futures for Autism” event in which Dallas teens partner with engineering students to practice social skills while participating in fun manufacturing-related design-build-test competitions.