Resumen:

Thermal gradients during metals additive manufacturing (AM) generate non-equilibrium and complex microstructures, particularly in multi-phase materials. Hence, most current adoptions of AM by various industry sectors continue to rely on alloys with a single dominating matrix phase only. My latest research demonstrates that the non-equilibrium state of as-printed duplex alloys can be regarded as an opportunity to engineer microstructures, rather than a challenge. By controlling the distribution and size of the second phase and generating customised interphase boundaries, superior mechanical and corrosion properties can be achieved. In this seminar, I will unveil some of microstructural complexities in a duplex stainless steel processed by laser powder bed fusion. As-printed microstructures exhibit significant deviations when compared to conventionally manufactured counterparts in terms of phase balance and morphology, elemental partitioning, and interface character distribution. Only a small fraction of austenite forms, and in the austenite-ferrite interfaces, ferrite grains are shown to have a higher tendency to terminate on (100) habit planes instead of crystallographically and energetically favoured (110) planes. A short post-AM heat treatment can harness the AM-induced metastability and defects to engineer duplex microstructures towards advanced mechanical properties

Bio:

Dr. Nima Haghdadi is a Senior Lecturer in the Department of Materials at Imperial College London, since February 2024. He also holds an adjunct senior lectureship at UNSW Sydney, where he was a Lecturer and postdoctoral research fellow from 2019 to 2024. Prior to that, he was a Deakin University Vice-Chancellor (Alfred-Deakin) Fellow and a Victoria Fellow, conducting research at Deakin University in Australia and the Max-Planck-Institut für Eisenforschung in Germany. An expert in physical metallurgy, Dr. Haghdadi has received numerous awards, including the prestigious FEI Cowley-Moodie award and the Acta Materialia student award. He has delivered several invited talks at international conferences such as Thermec, Rex&GG, and APICAM. Dr. Haghdadi’s research focuses on understanding microstructure-property relationships in metallic materials, particularly through thermo-mechanical processing and additive manufacturing. His team particularly specializes in interface and grain boundary engineering to enhance material performance and durability. Dr. Haghdadi serves as an editor for the Journal of Materials Science