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<p>The mechanical properties of additively manufactured Ti-6Al-4V are determined by its non-equilibrium α + β duplex solidification microstructure and inherent powder-derived initial defects, but their interaction under rapid thermal cycling remains unclear. Here, molecular dynamics (MD) simulations were used to construct atomic models with α/β interfaces and typical initial defects including voids and layered defects, revealing atomic-scale microstructural and defect evolution during melting, solidification, and tensile deformation. It is revealed that defect volume fraction, instead of geometric morphology, dominates the melting onset of the duplex alloy, accompanied by pronounced Al segregation at defect surfaces and α/β phase boundaries. Substrate temperature acts as a decisive factor regulating solidification microstructure: low temperature (373&#xa0;K) promotes Al segregation and twinning, while moderate temperature (843&#xa0;K) favors uniform fine duplex microstructures, and high temperature (1043&#xa0;K) stabilizes the β phase. Initial defects act as heterogeneous nucleation sites and induce microstructural inhomogeneity via local solute enrichment. Tensile simulations show yield strength decreases with increasing defect volume fraction, which is the dominant factor. This study establishes an atomic-scale correlation between initial defects, solidification microstructure, and mechanical properties, offering mechanistic guidance for optimizing powder quality and additive manufacturing processes optimization of Ti-6Al-4V components.</p> Graphical abstract <p></p>

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Defect-governed melting and microstructure evolution in additively manufactured Ti-6Al-4V: a molecular dynamics study

  • 期刊论文

  • 发表日期：

    2026年8月3日

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  • Xianghan Wang,
  • Frank Wendler,
  • Lei Shi,
  • Jianfeng Zhao,
  • Jinling Liu,
  • Xu Zhang

摘要

The mechanical properties of additively manufactured Ti-6Al-4V are determined by its non-equilibrium α + β duplex solidification microstructure and inherent powder-derived initial defects, but their interaction under rapid thermal cycling remains unclear. Here, molecular dynamics (MD) simulations were used to construct atomic models with α/β interfaces and typical initial defects including voids and layered defects, revealing atomic-scale microstructural and defect evolution during melting, solidification, and tensile deformation. It is revealed that defect volume fraction, instead of geometric morphology, dominates the melting onset of the duplex alloy, accompanied by pronounced Al segregation at defect surfaces and α/β phase boundaries. Substrate temperature acts as a decisive factor regulating solidification microstructure: low temperature (373 K) promotes Al segregation and twinning, while moderate temperature (843 K) favors uniform fine duplex microstructures, and high temperature (1043 K) stabilizes the β phase. Initial defects act as heterogeneous nucleation sites and induce microstructural inhomogeneity via local solute enrichment. Tensile simulations show yield strength decreases with increasing defect volume fraction, which is the dominant factor. This study establishes an atomic-scale correlation between initial defects, solidification microstructure, and mechanical properties, offering mechanistic guidance for optimizing powder quality and additive manufacturing processes optimization of Ti-6Al-4V components.

Graphical abstract