Abstract

A recent project entitled “Development of an Ecosystem for Qualification of Additive Manufacturing Processes and Materials in Aviation” demonstrated the inverse dependence of fatigue on pore number density in AM Ti-6Al-4V. The fatigue-based process window was much narrower than typically reported but explainable in terms of observed variations based on spatter rates and intermittent lack of melt pool overlap. A current “Institute for Model-Based Qualification & Certification of Additive Manufacturing (IMQCAM)” focuses on creating a numerical digital twin (DT) for predicting fatigue as a function of process parameters. We report on recent developments in modeling microstructure, texture and pores along with variations in heat treatment. We conclude that establishing a qualified materials process is feasible via an efficient survey of a limited domain of process space. In terms of predictability of fatigue, the limited data suggests that the scatter in life is smallest in the long crack (Paris Law) regime, intermediate for short cracks and largest for crack nucleation. This provides an important background for Uncertainty Quantification (UQ), which is a major focus for the IMQCAM team and which has already revealed a significant sensitivity to compositional variations, for example. Ultimately, we aim to create a probabilistic model of fatigue that connects the initiation, short-crack and long-crack phases. Support for this approach to fatigue is justified by analysis of experimental measurements of the separate stages and its stress scaling.

Support from multiple agencies is gratefully acknowledged, including NASA , DOE/BES, DOE /NNSA, ONR , NSF, OEA , Commonwealth of Pennsylvania, and Ametek. I am indebted to my many collaborators.

Brief bio: Rollett earned an MA in Metallurgy & Materials Science in 1980 from Cambridge and a PhD in Materials Engineering from Drexel in 1987. He has been a member of the Dept. of Materials Science & Engineering at Carnegie Mellon University since 1995 which included five years as Department Head at CMU . He is a University Professor and the Co-Director of the Next Manufacturing Center on additive manufacturing. Previously, he worked at the Los Alamos National Laboratory with five years as a Group Leader then Deputy Division Director. He has been a Fellow of ASM since 1996, Fellow of the Institute of Physics (UK) since 2004 and Fellow of TMS since 2011. He received the Cyril Stanley Smith Award from TMS in 2014, was elected as Member of Honor by the French Metallurgical Society in 2015 and then became the US Steel Professor of Metallurgical Engineering and Materials Science in 2017. He received the Cyril Stanley Smith Award from the International Conference on Recrystallization and Grain Growth in 2019 and the Hans Bunge Award from the Intl. Conf. on Textures of Materials (ICOTOM) in 2024. He was an

International Francqui Professor (Belgium) in 2022 and received the ASM Gold Medal in 2024. His research focuses on processing-microstructure-properties relationships with interests in additive manufacturing, the measurement and prediction of microstructural evolution, the relationship between microstructure and properties, especially three-dimensional effects, texture & anisotropy and the use of synchrotron x-rays.