Nonmetal interstitial solute segregation and its influence on stabilizing and strengthening of HCP Ti <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"> <mml:mrow> <mml:mo stretchy="true">(</mml:mo> <mml:mrow> <mml:mn mathvari

Ti is widely used because of its high strength-to-weight ratio, and twin boundaries (TBs) play a critical role in its mechanical performance. In particular, (101‾2) TB influenced the tensile deformation mechanisms of Ti. In this study, the behavior of nonmetallic interstitial solutes (NISs) within (101‾2) TB was examined using density functional theory calculations. Six types of nonmetallic elements (H, B, C, N, O, and F) and four types of interstitial sites (tetrahedral, octahedral, hexahedral, and crowdion) were considered. The aim of this study is to clarify the segregation and strengthening behavior of NISs at (101‾2) TB, that is the primary deformation TB in Ti, thereby providing guidance for the design of Ti alloys with excellent mechanical properties. Our results revealed that most NISs tend to segregate to (101‾2) TB, and some NISs enhance TB cohesion. Through ab initio tensile tests, detailed deformation behaviors, including elastic deformation, local distortion, and NIS migration were observed. These phenomena highlight the complex interplay between the atomic relaxation and mechanical properties. Additionally, a volumetric descriptor was proposed based on the polyhedral volume differences of bulk/TB and Ti with and without NIS, which shows potential as a predictive tool for segregation and strengthening energies. This analysis offers deeper insight into the influence of NISs on the deformation mechanisms of Ti alloys and the design of high-performance Ti alloys with tailored mechanical properties through NIS optimization at (101‾2) TB.