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<p>The mechanical performance of Ti<sub>2</sub>AlNb alloys is critically influenced by interstitial elements, yet their atomic-scale effects remain insufficiently understood. In this study, first-principles calculations were employed to systematically investigate the influence of four representative interstitial atoms (B, C, N, and O) on the structural and mechanical properties of O-phase and B<sub>2</sub>-phase in Ti<sub>2</sub>AlNb alloys, as well as on the O(001)/B<sub>2</sub>(110) interface. The results reveal that interstitial doping induces lattice expansion. Although O-phase and B<sub>2</sub>-phase each contain two distinct interstitial sites, the thermodynamic incorporation preference is consistent across both, following the sequence N &gt; C &gt; O &gt; B in O-phase and O &gt; B &gt; C &gt; N in B<sub>2</sub>-phase. Mechanically, all interstitials enhance the stiffness of the B<sub>2</sub>-phase but reduce its ductility, whereas nitrogen uniquely strengthens the O-phase, while interstitial doping generally improves its ductility. Furthermore, nitrogen exhibits a pronounced site preference near the O/B<sub>2</sub> interface and enhances interfacial cohesion by significantly increasing the work of separation through covalent bonding with neighboring Ti, Al, and Nb atoms. Experimental results demonstrate that the incorporation of nitrogen into Ti<sub>2</sub>AlNb alloys leads to a significant increase in tensile strength from 945 to 1092&#xa0;MPa, which can be primarily attributed to the combined effects of solid solution strengthening and grain refinement, and although a slight reduction in elongation is observed, the alloys still exhibit ductile fracture behavior. These findings elucidate the atomistic mechanisms by which interstitial species modulate mechanical behavior and provide a theoretical foundation for the targeted design of high-performance Ti<sub>2</sub>AlNb-based alloys with improved interfacial integrity.</p>

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The role of interstitial atoms in Ti2AlNb alloys: insights from first-principles calculations

  • 期刊论文

  • 发表日期：

    2026年1月20日

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  • Ziying Zhang,
  • Lianyong Xu,
  • Lei Zhao,
  • Yongdian Han,
  • Qiang Chen

摘要

The mechanical performance of Ti2AlNb alloys is critically influenced by interstitial elements, yet their atomic-scale effects remain insufficiently understood. In this study, first-principles calculations were employed to systematically investigate the influence of four representative interstitial atoms (B, C, N, and O) on the structural and mechanical properties of O-phase and B2-phase in Ti2AlNb alloys, as well as on the O(001)/B2(110) interface. The results reveal that interstitial doping induces lattice expansion. Although O-phase and B2-phase each contain two distinct interstitial sites, the thermodynamic incorporation preference is consistent across both, following the sequence N > C > O > B in O-phase and O > B > C > N in B2-phase. Mechanically, all interstitials enhance the stiffness of the B2-phase but reduce its ductility, whereas nitrogen uniquely strengthens the O-phase, while interstitial doping generally improves its ductility. Furthermore, nitrogen exhibits a pronounced site preference near the O/B2 interface and enhances interfacial cohesion by significantly increasing the work of separation through covalent bonding with neighboring Ti, Al, and Nb atoms. Experimental results demonstrate that the incorporation of nitrogen into Ti2AlNb alloys leads to a significant increase in tensile strength from 945 to 1092 MPa, which can be primarily attributed to the combined effects of solid solution strengthening and grain refinement, and although a slight reduction in elongation is observed, the alloys still exhibit ductile fracture behavior. These findings elucidate the atomistic mechanisms by which interstitial species modulate mechanical behavior and provide a theoretical foundation for the targeted design of high-performance Ti2AlNb-based alloys with improved interfacial integrity.