Phase separation with ordering in aged Fe-Ni-Mn medium entropy alloy
Phase separation with ordering in aged Fe-Ni-Mn medium entropy alloy
复制标题
DOI：
10.1016/j.actamat.2021.117487
复制
发表时间：
2021-11
期刊：
影响因子：
9.4
通讯作者：
F. Sun;G. Miyamoto;Yikun Liu;Y. Hayasaka;T. Furuhara
中科院分区：
文献类型：
--
作者：
F. Sun;G. Miyamoto;Yikun Liu;Y. Hayasaka;T. Furuhara
高熵和中熵合金目前正受到极大关注。理解元素间相互作用的短程有序和纳米尺度相分离是设计高熵合金时控制相稳定性的关键。在这项研究中，我们旨在利用球差校正扫描电子显微镜(Cs校正STEM)和三维原子探针(3DAP)等先进表征技术来阐明Fe-35Ni-35Mn(at%)中熵合金时效过程中的同步相分离和有序化。在500℃时效96h后，由于L100有序相的形成和相分离，出现了明显的时效硬化。在400℃或更短的时间时效，未观察到明显的有序相析出，但3DAP得到的径向分布函数表明，在同类元素附近观察到了镍和锰的富集，这一趋势对锰来说更强。这一结果表明，时效初期的相分离是由锰团簇引起的。建立了考虑L10有序结构的相稳定性统计热力学模型。用该模型进行的分析表明，在500℃的无序状态下，L100相是不可能相分离的，因此，在此温度下，L100相的形核应先于相分离。另一方面，即使在400℃时处于无序状态，相分离也是可能的，有序进一步增强了相分离。
High- and medium-entropy alloys are currently receiving significant attention. Understanding short-range ordering and nano-scaled phase separation concerning elemental interaction is a key to controlling phase stability for designing of high entropy alloys. In this study, we aim to clarify concurrent phase separation and ordering during aging of Fe-35Ni-35Mn (at%) medium-entropy alloy using advanced characterization techniques such as spherical aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM) and three-dimensional atom probe (3DAP). Obvious age hardening occurs after aging at 500 °C for 96 h due to the formation of L10ordered phase combined with phase separation. By aging at 400 °C or shorter time, obvious precipitation of the ordered phase is not detected but the radial distribution functions obtained by 3DAP present that enrichment of Ni and Mn nearby the same kinds of the element is observed, and this tendency is stronger for Mn. This result suggests that phase separation is induced by Mn clustering in the early stage of aging. A statistical thermodynamic model of phase stability considering L10ordered structure is developed. The analyses using the model suggest that phase separation is not possible in a disordered state at 500 °C, therefore, nucleation of the L10phase should precede phase separation at this temperature. On the other hand, phase separation is possible even in a disordered state at 400 °C, and ordering further enhances phase separation.