Engineering grain boundaries in metallic materials via additive manufacturing

Guest Speaker： Professor. Nima Haghdadi，Imperial College London, England

Inviter: Prof. Hongze Wang

Date&Time: Monday, 17th Nov.  15:00-16:30

Venue: Meeting Room 303, Special Materials Building

Biography:

Dr Nima Haghdadi is an Associate Professor in Metallurgy in the Department of Materials at Imperial College. He also holds an adjunct academic position with UNSW Sydney in Australia, where he previously was a lecturer, deputy group leader and postdoctoral research fellow from 2019 to 2024. Prior to that, Dr. Haghdadi held positions as a Deakin University Vice-Chancellor (Alfred-Deakin) Fellow and a Victoria Fellow from 2017 to 2019, during which he conducted the overseas part of his research at the Max-Planck-Institut für Eisenforschung GmbH in Germany.

Dr. Haghdadi is the recipient of numerous awards including the prestigious TFS Cowley-Moodie award for an outstanding contribution to physical sciences using electron microscopy, as well as the Acta Materialia student award. His contributions have been published in leading physical metallurgy journals as viewpoint, review and research articles, and he has presented numerous invited talks at international conferences, including Thermec, ACMM, PMS, Rex&GG, CAMS, PRICM, TMS and APICAM.

With a broad and deep expertise spanning fundamental discovery and applied industry research, Dr. Haghdadi's team aims to establish a conceptual bridge between microstructure-property relationships across thermo-mechanical processing and additive manufacturing pathways in various metallic materials systems with applications in aerospace, automotive, mining, energy, and biomedical sectors. Some of the materials of interest are advanced steels, Ni alloys, Ti alloys, Cu alloys, and high entropy alloys. His group's focus lies particularly on interface and grain boundary engineering and its impact on materials' performance and durability.

Abstract:

Microstructure engineering, i.e., the process of controlling microstructural features, can be achieved either during the additive manufacturing (AM) process itself (in-situ) or through subsequent post-processing steps (ex-situ). In AM, the material experiences repeated cycles of heating, cooling, and plastic deformation, presenting opportunities to strategically tailor these cycles. By leveraging this approach, the thermal and mechanical inputs, commonly known as 'heat and beat', can be precisely controlled to influence the microstructure of metals. This talk looks into how thermal hysteresis during AM can be exploited to achieve specific grain boundary crystallography and solute segregation. These in-situ optimizations not only eliminate the need for labour-intensive and costly ex-situ post-processing but also enhance the mechanical properties and corrosion resistance of the as-built components.