Ter-Isahakyan Artashes, Balk Thomas John
Department of Chemical and Materials Engineering, University of Kentucky, 177 F. Paul Anderson Tower, Lexington, KY 40506, USA.
Materials (Basel). 2023 Mar 19;16(6):2455. doi: 10.3390/ma16062455.
Investigation into non-equiatomic high-entropy alloys has grown in recent years due to questions about the role of entropy stabilization in forming single-phase solid solutions. Non-equiatomic alloys have been shown to retain the outstanding mechanical properties exhibited by their equiatomic counterparts and even improve electrical, thermal, and magnetic properties, albeit with relaxed composition bounds. However, much remains to understand the processing-structure-property relationships in all classes of so-called high-entropy alloys (HEAs). Here, we are motivated by the natural phenomena of crystal growth and equilibrium conditions to introduce a method of HEA development where controlled processing conditions determine the most probable and stable composition. This is demonstrated by cooling an equiatomic CrMnFeCoNiCu alloy from the melt steadily over 3 days (cooling rate ~4 °C/h). The result is an alloy containing large Cr-rich precipitates and an almost Cr-free matrix exhibiting compositions within the MnFeCoNiCu system (with trace amounts of Cr). From this juncture, it is argued that the most stable composition is within the CrMnFeCoNiCu system rather than the CrMnFeCoNi system. With further optimization and evaluation, a unique non-equiatomic alloy, MnFeCoNiCu, is derived. The alloy solidifies and recrystallizes into a single-phase face-centered cubic (FCC) polycrystal. In addition to possible applications where Invar is currently utilized, this alloy can be used in fundamental studies that contrast its behavior with its equiatomic counterpart and shed light on the development of HEAs.
近年来，由于对熵稳定在形成单相固溶体中的作用存在疑问，对非等原子高熵合金的研究不断增加。已表明非等原子合金保留了其等原子对应物所具有的优异机械性能，甚至改善了电学、热学和磁学性能，尽管其成分范围有所放宽。然而，在理解所有所谓的高熵合金（HEA）的加工-结构-性能关系方面仍有许多工作要做。在此，我们受晶体生长和平衡条件的自然现象启发，引入一种高熵合金开发方法，其中受控的加工条件决定了最可能和稳定的成分。通过将等原子CrMnFeCoNiCu合金从熔体中以约4℃/小时的冷却速率在3天内稳定冷却来证明这一点。结果得到一种合金，其含有大量富Cr析出物和几乎不含Cr的基体，其成分在MnFeCoNiCu体系内（含有痕量的Cr）。由此可以认为，最稳定的成分在CrMnFeCoNiCu体系内而非CrMnFeCoNi体系内。通过进一步优化和评估，得到了一种独特的非等原子合金MnFeCoNiCu。该合金凝固并再结晶为单相面心立方（FCC）多晶体。除了目前使用因瓦合金的可能应用外，这种合金可用于基础研究，将其行为与其等原子对应物进行对比，并为高熵合金的开发提供启示。
