【摘要】 采用第一性原理方法系统研究了不同六角结构金属中基面到柱面的取向转变过程及合金化影响。结果表明,在不同六角结构金属中,取向转变需要不同的激发能,其中Mg的激发能最低,而Os最高;取向转变过程由剪切变形和原子重排2部分构成。在Mg中,原子重排贡献了激发能的主要部分,而在Ti中,当剪切变形足够大时,随后的原子重排为能量下降过程。合金元素主要影响镁合金中的纯剪切变形部分,而在钛合金中,主要影响原子重排部分;在具有一定的剪切变形量或原子重排量的条件下,合金元素对后续激发能的影响较复杂。更多还原

【Abstract】 In hexagonal metals and alloys, deformation twinning plays an important role, because it is closely relevant to the mechanical behaviors. Recent studies have proposed a new twinning mode via direct lattice reorientation, which results in the basal/prismatic boundary, however, some important details remain unanswered, e.g., the twinning path and alloying effect. In this work, first principles calculations were employed to systematically study the reorientation process from basal to prismatic orientation in hexagonal metals and corresponding alloying effect. The result indicates that different activation energies are required to reorient in various hexagonal metals, and among them, the energy in Mg is the lowest and Os is the highest. Shear and shuffle components compose the reorientation process, where the shuffle component always contributes a significant part of the activation energy in Mg, whereas in Ti with sufficient shear strain, subsequent transition becomes energy-downhill. The pure shear was effected by alloying elements in Mg alloys, but pure shuffle in Ti alloys. Under certain shear or shuffle, subsequent activation energy has a complex dependence on alloying elements.更多还原