Lee Hsun Lecture Series （239-L168）

Topic: Design and control of solidification microstructure for directionally solidified superalloys

Speaker: Prof. Hongbiao DONG

School of Metallurgy and Materials, University of Birmingham, Birmingham, B15 2TT, UK

Time: 10:00-12:00, (Thur.) Aug. 27^th, 2026

Venue: Room 468, Lee Hsun Building, IMR CAS

Abstract:

Dendritic morphology is a defining feature of solidified metallic alloys, with primary dendrite arm spacing (PDAS) and packing order exerting a strong influence on microsegregation, defect formation, and subsequent heat-treatment response. Here, we introduce shape-limited primary spacing (SLPS), a supervised machine-learning method for rapid, image-based quantification of local PDAS and dendrite packing order in directionally solidified microstructures. Applied to experimental Ni-based alloy microstructures and complementary solutal dendrite simulations, SLPS reveals that hexagonally ordered dendrite arrays are associated with near steady-state tip growth under spatially homogeneous liquid composition. The admissible range of local PDAS is governed by local growth-rate variations and the capacity of the array to adjust laterally to thermal–solutal gradients. Simulations comparing square and hexagonal packing in transverse sections show that hexagonal arrays accommodate local spacing variations more effectively, promoted by secondary-arm development and tertiary-to-primary branching. As a result, hexagonally packed arrays develop finer PDAS than square-packed arrays. These findings provide a mechanistic basis for process design strategies that promote hexagonally ordered, close-packed dendrite arrays, offering a route to finer microstructures, reduced microsegregation, lower defect-grain susceptibility, and shorter solution heat-treatment times.

Biograph:

Professor Hongbiao Dong is 125th Anniversary Chair, Professor of Materials Engineering at the University of Birmingham, a Fellow of RoyalAcademy of Engineering, the President of Association of British Chinese Professors (ABCP), an outstanding engineer who has made ploneering and significant contributions in numerical modeling of metal processing and digtal transformation of metal industry. He is internationally renowned for modelling work and its application in metals and manufacturing. His research aims tobring knowledge- inspired decision making to the production routes of high value-added engineering structures, such as aero-engine compo-nents, deep-sea oil and gas transport systems. He chaired STFC-ISIS Engineering User Committee and a member of Steering Commitee of theEuropean Materials Modelling Council, a recipient of the Metrology for World Class Manufacturing award and a Royal Society Industry Fellow at Rolls-Royce Precision Casting Facility.