Abstract The mechanical properties of hexagonal Ti alloys depend substantially on the glide of a > type screw dislocations. The configurations and stabilities of these line defects are, however, known only in pure Ti and Ti + O solutions, where the locking-unlocking mechanism and a strong pinning effect control their activity. In this study, we investigated the unclear, screw dislocation mediated solution strengthening of substitutional α-Ti alloys. To this end, a first principle computational scheme was used to determine the structures and energies of the considered line defects during planar and cross-slip processes in the vicinity of the solute element. Two phenomena were determined that are crucial in terms of plastic deformation: (i) enhanced polymorphism of the dislocation cores leading to multiple new core configurations, and (ii) relatively large positive and negative interaction energies between the solutes and the line defects. Both these effects are strongly affected by the valence configuration of the alloying elements. Due to their pronounced structure and energy variations, dislocation planar and cross slip processes can occur under different scenarios, through diverse non-planar core geometries. Accordingly, an improvement in material strength is related to the overall energy amplitude of the dislocation states that can occur in the neighbourhood of the alloying element, which agrees well with experimental data. The calculations performed also indicate In as a potential alloy element for improving both the strength and ductility of Ti by stabilizing a special, compact core geometry able to spread on an arbitrary glide plane with a low energy barrier. All of the above effects are discussed in terms of the physical factors (solute size misfit, stacking fault energy and electronic structure) that affect the energy and geometry of dislocation cores.

中文翻译：

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替代α-Ti合金的螺位错介导固溶强化 - 第一性原理研究

摘要 六方钛合金的力学性能主要取决于a > 型螺型位错的滑动。然而，这些线缺陷的配置和稳定性仅在纯 Ti 和 Ti + O 溶液中为人所知，其中锁定-解锁机制和强大的钉扎效应控制着它们的活性。在这项研究中，我们研究了替代性 α-Ti 合金的不清楚的、螺旋位错介导的固溶强化。为此，使用第一原理计算方案来确定在溶质元素附近的平面和交叉滑移过程中所考虑的线缺陷的结构和能量。确定了两种对塑性变形至关重要的现象：（i）位错核的多态性增强，导致多个新的核配置，(ii) 溶质和线缺陷之间相对较大的正负相互作用能。这两种效应都受到合金元素价态构型的强烈影响。由于它们明显的结构和能量变化，位错平面和交叉滑移过程可以在不同的情况下通过不同的非平面核心几何形状发生。因此，材料强度的提高与可能发生在合金元素附近的位错状态的整体能量幅度有关，这与实验数据非常吻合。进行的计算还表明，In 是一种潜在的合金元素，可通过稳定一种特殊的、紧凑的核心几何形状来提高 Ti 的强度和延展性，该几何形状能够在具有低能垒的任意滑动平面上展开。