Defect closure behavior and microstructural evolution of Ti-6Al-4V alloy fabricated by electron beam wire-feed additive manufacturing during hot compression and hot isostatic pressing
Abstract
Additive manufacturing (AM) holds promise for fabricating complex structural components, but metallurgical defects generated during deposition remain a major hurdle. Particularly lacking is a detailed understanding of how internal defects evolve and close under post-processing thermo-mechanical treatment. In this work, the defect closure behavior in AMed Ti-6Al-4V after hot compression and hot isostatic pressing (HIP) treatment was studied using industrial X-ray computed tomography (CT) and finite element (FE) simulations. The effect of defects on the evolution of their nearby microstructures was also discussed. Results show that defects follow distinct closure pathways under the two methods, i.e. spherical defects → flattened into ellipsoidal voids → closure → welding during hot compression, and spherical defect → shrinkage → collapse → closure → welding during HIP. From CT and FE data, we determine a critical true strain of 0.4 in hot compression is sufficient for defect elimination. Stress-strain heterogeneity is pronounced near defects, and microstructure differs markedly between defective and defect-free zones. After hot compression, defective regions show a mixed microstructure while defect-free regions form a basket-weave microstructure. After HIP, defective zones evolve to a fully equiaxed microstructure, while defect-free regions retain a basket-weave morphology. The disparities stem from different recrystallization mechanisms, dynamic recrystallization in hot compression versus creep recrystallization in HIP. This work fills a knowledge gap in how defects close under thermal deformation in AMed Ti alloys and offers practical insights for optimizing post-processing routes to improve AM quality.
Document Type
Journal Article
Date of Publication
1-1-2026
Volume
949
Publication Title
Materials Science and Engineering: A
Publisher
Elsevier
School
Centre for Advanced Materials and Manufacturing / School of Engineering
Funders
National Natural Science Foundation of China (52271108) / Natural Science Foundation of Shanghai (21ZR1445100) / Foundation of Xi'an Key Laboratory of High-Performance Titanium Alloy (NIN-HTL-2022-02) / The National Key Research and Development Program of China (2022YFB3705600)
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Comments
Wang, M., Hu, J., Yang, Y., Zhang, K., Wang, H., Han, F., Li, G., Huang, A., & Zhang, L. (2025). Defect closure behavior and microstructural evolution of Ti-6Al-4V alloy fabricated by electron beam wire-feed additive manufacturing during hot compression and hot isostatic pressing. Materials Science and Engineering: A, 949, 149387. https://doi.org/10.1016/j.msea.2025.149387