Dr. Xiaoyuan Lou, Associate Professor in School of Nuclear Engineering and School of Materials Engineering at Purdue University will give a seminar titled "Twin-related Grain Boundary Engineering for Laser Additive Manufacturing" to the interested faculty and students at Discovery Park.

Abstract

Laser based additive manufacturing (AM), such as laser powder bed fusion (L-PBF) and laser directed energy deposition (L-DED), has enabled unprecedented flexibility in fabricating complex, high‑performance components, but often produces heterogeneous grain structures and non‑ideal grain boundary networks that limit the performance and reliability in service environments. In comparison, coherent twin boundaries offer greater thermal, chemical and mechanical stabilities than dislocation structures and random grain boundaries.  Twin boundaries have been demonstrated to offer better fatigue resistance, corrosion/oxidation resistance, creep resistance, and less prone to detrimental GB precipitates under thermal aging. Conventional manufacturing of wrought products typically use the multi-step thermomechanical process to enable twin-related grain boundary engineering (GBE). However without complex thermomechanical treatment, a strategy to create high-density twin boundaries during laser AM has not been established.

This talk will provide a broad overview of our continuing efforts to understand the formation mechanisms of twins under rapid laser solidification and post-AM heat treatment. Attention will be given to how process variables and alloy composition influence twin formation and grain boundary character distributions. In particular, the talk will discuss the fundamentals of microstructure development related to two main strategies, including (1) recrystallization-induced twinning, (2) phase transformation-induced twinning. We demonstrated for the first time that GBE of LPBF AM 316L SS, with twin boundary fraction exceeding the best practice of conventional GBE wrought 316L SS, can be achieved.

Bio

Dr. Xiaoyuan Lou is an associate professor in School of Nuclear Engineering and School of Materials Engineering at Purdue University. He earned his Ph.D. in materials science and engineering from Georgia Institute of Technology. Before joining Purdue, he was an associate professor at Auburn University and a lead material scientist at GE Global Research. Dr. Lou’s work involves understanding the damage and degradation mechanisms of metallic alloys in nuclear environments, and developing advanced manufacturing methods and alloys for extreme environments. Dr. Lou was recognized with two times for “Best Paper Award” by Journal of Nuclear Materials (2019, 2023), "Top Cited Paper Award" by International Journal of Plasticity, three GE Corporate awards, Outstanding Faculty Teaching Award from Auburn University College of Engineering, and Paul C. Zmola Scholar of Nuclear Engineering Award from Purdue Nuclear Engineering.