Dislocation core structure and motion in pure titanium and titanium alloys: A first-principles study
Dislocation core structure and motion in pure titanium and titanium alloys: A first-principles study
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DOI：
10.1016/j.commatsci.2021.111081
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发表时间：
2022-02
影响因子：
3.3
通讯作者：
T. Tsuru;M. Itakura;M. Yamaguchi;Chihiro Watanabe;H. Miura
中科院分区：
文献类型：
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作者：
T. Tsuru;M. Itakura;M. Yamaguchi;Chihiro Watanabe;H. Miura
由于α相中的合金化元素，某些钛(Ti)合金的变形方式与纯钛不同。本文用密度泛函理论方法研究了纯钛中所有可能的滑移模式以及Al和V作为典型添加元素对α-Ti合金中位错运动的影响。层错能计算表明，Al和V溶质都降低了基面的层错能。相反，Al溶质增加了棱柱面内的SF能量，使不同平面上的滑移运动更具可比性。随后进行了密度泛函理论计算来模拟位错核结构。各种可能的位错核结构与位错在不同滑移面的位错滑移势垒之间转变的能量图景阐明了纯钛中位错运动的本质；I)棱柱核的能量高于最稳定的金字塔核，因此位错在棱柱面移动时需要克服交叉滑移的能垒(22.8 mev/b)；ii)棱柱核和基核之间的能量差较大(127 mev/b)，表明基滑移不被激活；iii)然而，一旦位错稳定地存在于基面，基面内的Peierls运动势垒就不再那么高(16 mev/b)。对溶质周围位错核的直接计算表明，Al和V溶质都通过减小柱状和基面晶核之间的能量差来促进位错在基面上的运动。因此，溶质的影响表征了纯钛和α-Ti合金变形方式的不同。
The deformation mode of some titanium (Ti) alloys differs from that of pure Ti due to alloying elements in the α-phase. Herein, we investigated all possible slip modes in pure Ti and the effects of Al and V solutes as typical additive elements on the dislocation motion in α-Ti alloys using density functional theory (DFT) calculations. The stacking fault (SF) energy calculations indicated that both Al and V solutes reduce the SF energy in the basal plane. In contrast, Al solute increases the SF energy in the prismatic plane, making the slip motion in different planes more comparable. DFT calculations were subsequently carried out to simulate dislocation core structures. The energy landscape of the transition between all possible dislocation core structures and the barriers for dislocation glide in various slip planes clarified the nature of dislocation motion in pure Ti; i) the energy of prismatic core is higher than the most stable pyramidal core, and thereby dislocations need to overcome the energy barrier of the cross-slip (22.8 meV/b) when they move in the prismatic plane, ii) the energy difference between the prismatic and basal cores is higher (127 meV/b), that indicates the basal slip does not activate, iii) however, the Peierls barrier for motion in the basal plane is not as high (16 meV/b) once the dislocation exists stably in the basal plane. Direct calculations for the dislocation core around solutes revealed that both Al and V solutes facilitate dislocation motion in the basal plane by reducing the energy difference between the prismatic and basal cores. Thus, the effect of solutes characterizes the difference in the deformation mode of pure Ti and α-Ti alloys.