论文标题
相位稳定性的起源在Fe中，长期堆叠顺序作为环状$γ$ - $ε$ martensenitic Transform的中间阶段
Origin of phase stability in Fe with long-period stacking order as an intermediate phase in cyclic $γ$-$ε$ martensitic transformation
论文作者
论文摘要
Fe-MN-SI类的合金具有带面部为中心的立方〜（FCC）结构的$γ$相位和具有六角形封闭式（HCP）结构的$γ$相位之间的可逆Martensitic转换。在变形诱导的$γ$ - $ε$转换期间，我们确定了一个与$ε$相同的阶段。在这个新阶段，电子衍射点位于与2H结构的$ε$（HCP）相对应的$ \ {$ \ {$ \ {$ \ {$ \ {$ \ {$ \ {$ 0002 $ \} $平面，这暗示了长期堆叠订单（LPSO）。为了理解堆叠模式并探索LPSO相的可能存在，作为$γ$和$ε$阶段之间的中间体，使用第一原理计算，使用具有旋转形式的普遍梯度近似值的密度函数理论中的普遍梯度近似形式来检查铁的各种结构多型铁的相位稳定性。我们发现，在候选LPSO结构中最稳定的抗铁磁序列6h $ _2 $结构在$ε$相位上最稳定，这表明观察到的类似LPSO的相位采用6H $ _2 $结构。此外，我们确定相位稳定性可以归因于状态密度（接近费米水平）的山谷深度。
A class of Fe-Mn-Si-based alloys exhibits a reversible martensitic transformation between the $γ$ phase with a face-centered cubic~(fcc) structure and an $ε$ phase with a hexagonal close-packed (hcp) structure. During the deformation-induced $γ$--$ε$ transformation, we identified a phase that is different from the $ε$ phase. In this new phase, the electron diffraction spots are located at the 1/3 positions that correspond to the $\{$0002$\}$ plane of the $ε$ (hcp) phase with 2H structure, which suggests long-period stacking order (LPSO). To understand the stacking pattern and explore the possible existence of an LPSO phase as an intermediate between the $γ$ and $ε$ phases, the phase stability of various structural polytypes of iron was examined using first-principles calculations with a spin-polarized form of the generalized gradient approximation in density functional theory. We found that an antiferromagnetic ordered 6H$_2$ structure is the most stable among the candidate LPSO structures and is energetically close to the $ε$ phase, which suggests that the observed LPSO-like phase adopts the 6H$_2$ structure. Furthermore, we determined that the phase stability can be attributed to the valley depth in the density of states, close to the Fermi level.
