非金属溶质C、H、O和N对α型钛合金基面滑移的影响

Effects of nonmetallic solutes C,H,O and N on basal slip in α-Ti alloys

采用基于密度泛函理论的第一性原理方法,研究了非金属溶质C、H、O和N对α型Ti合金(0001)[11 20]和(0001)[10 10]基面滑移的影响。研究结果表明,非金属原子使(0001)[10 10]基面滑移的广义层错能降低。其中,不稳定层错能γus的降低将导致该方向滑移的运动性能增强,而内禀层错能的降低将有利于I2层错的形成。对于(0001)[11 20]基面滑移,除H原子外,C、N和O原子都使Ti合金的广义层错能升高,这将使基面在[11 20]方向上滑移的能垒增加,促使该方向上的全位错向其他方向分解。通过进一步对Ti合金的Bader电荷、差分电荷密度分布和局域态密度的计算,从微观上分析了非金属溶质原子对Ti合金基面滑移的影响。电子结构的研究表明,非金属原子X(X=C、H、O和N)与其邻近的Ti原子之间形成强度稳定的TiX共价键,其对滑移过程起着重要的作用。

The effects of nonmetallic solute atoms including C, H, O and N on （0001）[1120] and （0001）[1010] basal slip ofα-Ti were investigated by first-principles method based on density func-tional theory. The calculation results showed that nonmetallic solutes C, H, O and N atoms de-creased the generalized stacking fault energy （GSFE） of the （0001）[1010] basal slip. The re-duced unstable stacking fault energy （γus ） resulted in the improvement in mobility of slip, while the reduction of intrinsic stacking fault energy could facilitate the formation of stacking faults I2 . Other than H atom, the C, N and O atoms increased GSFE of the （ 0001 ） [ 1120 ] basal slip, implying that the increased energy barriers of （0001）[1120] basal slip prompted the dislocation dissociation. Further more, Bader charge, differential charge density distribution and local density of states （ LDOS） were given to reveal the micro-mechanism for effects of nonmetallic solutes on basal slip. It was showed that stable Ti-X （ X = C、H、O and N） covalent bonds played an essential role in basal slip.