Achieving high performance low-cost Co-free FeMnCrNi-based medium entropy alloys via multiple synergistic strategies

Yuhang Shi, Jiaqing Wang, Pengfei Yun, Ke Tang, Liangbin Chen, Ran Wei, Jin Tian, Yake Wu, Feng Jiang

博士生史雨航第一作者，许昌学院陈良斌博士和本单位江峰教授为共同通讯作者， 郑州大学魏然副教授、本单位吴亚科副教授、这边毕业的田谨博士、王嘉庆硕士、在读博士生贠鹏飞为共同作者，  感谢各位的努力！

摘要：

通过合金化0.4%钛，同时选择合适的镍/铬比例和碳含量，采用热机械加工工艺，开发了一种低成本且具有良好综合机械性能的无钴（Fe40Mn40Cr10Ni10）96.6C3Ti0.4中熵合金（MEA）。该（Fe40Mn40Cr10Ni10）96.6C3Ti0.4 MEA经过冷轧处理，随后在600℃下退火2小时，形成一个非再结晶的面心立方基体，其中含有高密度位错、孪晶、微带和纳米级碳化物。在600℃下退火的MEA表现出优异的屈服强度和极限强度，分别为298 K时1013 MPa和1171 MPa，77 K时1339 MPa和1526 MPa，且伸长率不低于15%。理论和定量分析表明，设计合金的变形行为涉及激活位错和孪晶，主要增强的屈服强度源于较高的晶界、位错和沉淀强化。本研究为设计低成本的高性能H/MEA提供了启示。

Abstract

A low-cost Co-free (Fe40Mn40Cr10Ni10)96.6C3Ti0.4 medium entropy alloy (MEA) with the comprehensive mechanical performance is developed by alloying 0.4% Ti simultaneously selecting the appropriate Ni/Cr ratio and carbon content and using an elaborate thermo-mechanical processing. The (Fe40Mn40Cr10Ni10)96.6C3Ti0.4 MEA subjected to cold rolling and subsequent annealing at 600 ℃ for 2h, comprises a nonrecrystallized FCC matrix containing high-density dislocations, twins, micro-bands and nano-sized carbides. The MEA annealed at 600 ℃ exhibits exceptional yield and ultimate strength of 1013 MPa and 1171 MPa at 298 K and 1339 MPa and 1526 MPa at 77 K, respectively, with a consistent elongation not less than 15%. Theoretical and quantitative analyses reveal that the deformation behavior of the designed alloy involving with activating dislocations and twins, and presents the enhanced yield strength primarily originates from higher grain boundary, dislocation and precipitation strengthening. This study sheds light on designing cost-effective high-performance H/MEAs