FCC结构高熵合金微观组织与变形机制调控的碳合金化效应

High-entropy alloys (HEAs) with single face-centered cubic structure have an unique structure and properties, but the poor room-temperature strength will hinder their application as high performance structure materials. There is an urgent need to develop methods and theories that can effectively improve strength and maintain good plasticity. In the present proposal, a single FCC structured Fe40Mn40Co10Cr10 HEA in which dislocation strengthen is the dominant deformation mechanism at room temperature was selected as a starting material. By adding supersaturated interstitial carbon atom into this HEA, the dislocation resistance was improved through solid solution strengthening, the stacking fault energy and twin formation ability were changed. The dominant deformation mechanism of HEA would be transformed into deformation twining while increasing the strength and ductility; Cold deformation combined with low temperature Aging were occupied to introduce fine uniform second phase carbides in the matrix to further enhance the strength of the alloy and maintain good plasticity, overcoming the strength–ductility trade-off. The carbon alloying effect on the microstructure and deformation mechanism of high entropy alloy will be investigated and elucidated, including the interaction and transition behavior of solid solution carburizing and aging precipitation carbide with dislocation and twin deformation. Comprehensive application of multiple mechanisms i.e. interstitial solid-solution strengthening, deformation strengthening, precipitation strengthening, and twinning-induced plasticity were adopted for FCC high entropy alloy toughening. This work will enrich FCC HEAs toughening theory, provide the necessary support for their industrial applications.

单一FCC结构高熵合金具有独特的结构与性能，但室温强度不足严重阻碍了其工程应用，迫切需要发展能有效提高强度并保持较好塑性的方法和理论。本项目拟从能固溶大量碳原子且室温下位错强化机制主导其塑性变形的单一FCC结构Fe40Mn40Co10Cr10高熵合金出发，通过添加过饱和间隙碳原子固溶强化提高位错阻力和孪晶形成能力，使其以变形孪晶机制为主导而同时提高合金的强度和塑性；继续通过冷变形结合低温时效在基体中引入细小均匀的第二相碳化物来进一步提高合金的强度并维持较好的塑性，突破传统的强度-塑性倒置关系。阐明高熵合金微观组织与变形机制调控的碳合金化效应，包括固溶碳和时效析出碳化物与位错、孪晶的交互作用及变形机制的转换行为。综合应用间隙固溶强化、形变强化、第二相碳化物析出强化、孪晶诱发塑性强韧化等机制来实现FCC高熵合金的强韧化，丰富FCC高熵合金的强韧化理论，并为其下一步的工程应用提供有效的支撑。

单一FCC结构高熵合金具有独特的结构与性能，但室温强度不足严重阻碍了其工程应用，迫切需要发展能有效提高强度并保持较好塑性的方法和理论。以Fe40Mn40Co10Cr10合金为基础，研究了：添加不同C含量的合金的不同室温力学性能；不同C含量Fe40Mn40Co10Cr10合金在不同温度下的韧脆转变行为；对于含有3.3C的合金进行表面滚压处理获得梯度结构材料表现出良好的强度塑性配合；采用磁悬浮熔炼10Kg级别大铸锭，结合热锻和冷轧工艺优化组织性能，获得具有良好强塑性配合的大尺寸合金材料；在（Fe40Mn40Cr10Co10）96.7C3.3合金中添加少量Ti，结合热锻、冷轧、时效处理，得到纳米和微米尺度的第二相碳化物，研究室温和液氮温度的力学性能以及变形孪晶形成机制；采用内氧化和粉末锻造工艺制备出具有氧化物弥散增强的Fe40Mn40Cr10Co10的高性能合金；综合应用了间隙固溶强化、细晶强化、形变强化、第二相碳化物析出强化、孪晶诱发塑性强韧化等机制来实现FCC高熵合金的强韧化，获得的Ti掺杂(Fe40Mn40Co10Cr10）96.7C3.3合金在室温时表现出551Mpa的屈服强度、1Gpa的抗拉强度和50%的延伸率，在液氮温度时合金有高达1Gpa屈服强度和50%的断裂延伸率，突破了传统合金的强度-塑性倒置关系。同时解释了C原子辅助钉扎位错促进变形孪晶形成的机制，丰富了FCC高熵合金的强韧化理论。另外设计了三种主要成分为FeCoCrNiAlTi的双沉淀相强化FCC型高熵合金，其屈服强度均高于1.0 GPa，抗拉强度可达到1.4Gpa-1.6GPa，延伸率可达到13-38%，性能超越了目前绝大多数的沉淀强化FCC型高熵合金。还系统地研究了铝合金化和热机械处理对等原子比的VCoNi中熵合金组织和力学性能的影响，获得屈服强度超过1GPa、延伸率20%的高性能中熵合金，在此基础上研究VCoNi中熵合金中快速多样的相演化。已经在Scripta Mater（1）、MSEA（6）、Mater Lett（1）、JMST (2)等国际学术期刊上发表论文10篇，项目负责人均为通讯作者（6篇）或共同通讯作者（4篇），相关研究内容获得授权国家发明专利5项，培养硕士生、博士生多名,研究结果受到了同行的关注和引用。