Investigating synergistic effects of process-induced defects and α phase substructures on the mechanical response of additively manufactured Ti-6Al-4V alloy via an integrated numerical framework

Hanqing Liu; Fabien Briffod; Takayuki Shiraiwa

doi:10.1016/j.msea.2026.150551

ジャーナル論文 Investigating synergistic effects of process-induced defects and α phase substructures on the mechanical response of additively manufactured Ti-6Al-4V alloy via an integrated numerical framework

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Hanqing Liu, Fabien Briffod, Takayuki Shiraiwa. Investigating synergistic effects of process-induced defects and α phase substructures on the mechanical response of additively manufactured Ti-6Al-4V alloy via an integrated numerical framework. Materials Science and Engineering: A. 2026, 971 (), 150551. https://doi.org/10.1016/j.msea.2026.150551

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(abstract)

Laser powder bed fusion (LPBF)-fabricated Ti-6Al-4V alloys are characterized by complex α-lath substructures and inherent process-induced defects. While numerical investigations are prevalent, conventional models often oversimplify microstructural morphologies and defects, leading to deviations in predicting failure mechanisms. In this study, a novel approach integrating cellular automaton (CA) with an algorithm-based structure generation method is proposed to address these limitations. In this framework, the CA technique is first employed to simulate the growth of prior-β columnar grains. Subsequently, an ellipse-fitting method is developed to construct the α-lath substructure, where the β-to-α phase transformation is achieved based on the Burgers orientation relationship (BOR). The Monte Carlo method is utilized to construct an irregular defect based on experimental characteristics. Through a comparative study between observations and crystal plasticity finite element (CPFE) simulations, the synergistic roles of the α-lath substructure and defects on the resulting tensile responses are evaluated. It is found that basal and pyramidal 〈a〉 slip systems might be responsible for the crack initiation from the defect tips. Neglecting α-lath substructure results in a stress distribution overly dependent on prior-β grain boundaries and a marked underestimation of local stress/strain concentrations. The presence of defects is harmful to structural integrity and facilitate strain localization between defects, thereby accelerating the onset of localized failure and resulting in a zigzag-shaped fracture surface. The proposed microstructure construction strategy addresses the inherent shortcomings of traditional modeling methods and provides a robust tool for evaluating the mechanical behavior of additively manufactured metallic alloys.

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