Co-Cr-Fe-Ni基多主元高熵合金的相平衡及析出强化机理研究

High entropy alloys, which are some kinds of newly alloys based on multi-component design concept, are widely concerned because of their excellent performance. Precipitation of dispersed second phase particles is one of the most important methods to enhance the properties of the high entropy alloys. However, as a new type of alloy, the phase stability, phase transformation, precipitation strengthening behavior and mechanism in high entropy alloys are not well understood. The present project will experimentally investigate the effect of annealing, cold rolling and aging treatment on the precipitation morphology and mechanical properties of the Co-Cr-Fe-Ni-M(M=Al, Ti, Mn) multi-component high entropy alloys. The phase diagram in central region of the related quaternary and quinary system in Co-Cr-Fe-Ni-based multi-component high entropy alloys will be experimentally determined and thermodynamically assessed. And the stability of precipitated phase will be analyzed. Based on optimized thermodynamic and dynamic databases, a precipitation diffusion kinetic model will be built to simulate the precipitation process in the high entropy alloys. Moreover, atomic simulation based on Second Nearest-Neighbor Modified Embedded-Atom Method will be performed to analyze the dislocation slip behavior and the influence of the second phase precipitation in high entropy alloys. With the experiment data and simulation results, the precipitation strengthening mechanism in the Co-Cr-Fe-Ni-based high entropy alloys will be analyzed. These would lay the foundation for the composition design and process design of high entropy alloys and promote the application of high entropy alloys.

基于多主元设计理念的高熵合金因其优异的性能而受到广泛关注。析出弥散的第二相粒子是强化高熵合金的最重要方法之一。但作为一个新型的合金领域，目前对高熵合金的相稳定性、相变规律、第二相析出动力学、析出强化规律及其机理还不了解。本课题将实验研究平衡退火、冷轧和时效处理对Co-Cr-Fe-Ni-M（M=Al、Ti、Mn）多主元高熵合金析出相类型、形貌和力学性能的影响规律；实验测定相关四元系和五元系中心区域的平衡相图和垂直截面并进行热力学评估，并分析析出相的稳定性；基于优化的热/动力学数据库，建立扩散析出动力学模型，模拟高熵合金第二相的析出过程，并结合基于考虑次邻近原子交互作用的改进式嵌入原子方法对合金中位错滑移行为及析出第二相的影响进行原子级模拟，解析Co-Cr-Fe-Ni基高熵合金的析出强化机理。这将为高熵合金的成分设计和加工工艺设计奠定基础，推动高熵合金的应用。

本项目针对Co-Cr-Fe-Ni-M系高熵合金的热力学及动力学基础问题，采用实验研究与理论计算相结合的方法，对相关合金体系的平衡相组成、显微组织、扩散行为及力学性能进行了系统研究，获得了Cr-Fe-Ni-Co/Al、Co-Fe-Mn-Ni、Co-Cr-Fe-Ni-Al/Mn/Ti/Nb、Cr-Fe-Ni-Al-Mn/Ti等体系中心区域在800和1000℃的平衡相组成、各相的成分范围、组织特征、升温过程中的相转变和相稳定性等信息，确定了各成分合金通过热处理析出强化的可能性；明确了合金成分、退火温度、退火时间等参数与合金组织及显微硬度等力学性能的之间的联系；分析了Co-Cr-Fe-Ni-M系高熵合金中的元素扩散行为、扩散动力学规律及强硬化机理。截止目前，项目资助的相关研究成果在国内外期刊上发表学术论文13篇，参加国内外学术会议22人次，做口头报告5次，申请国家发明专利3件，获得中国有色金属工业科学技术奖三等奖1项，培养已毕业硕士研究生6人。很好地完成了既定研究计划，达到了预期目标。项目的开展为Co-Cr-Fe-Ni-M系高熵合金的成分设计及组织性能调控提供依据。