摘要
高熵合金具有高的混合熵、缓慢的扩散和严重的晶格畸变等特性,合金具有简单的组织结构和优异的综合性能,这为开发新型合金体系提供了广阔的发展思路。共晶高熵合金具有流动性好、凝固组织成分相对均匀、铸造缺陷少、组织可调控性等优点,可制备大尺寸高熵合金锭,因此共晶高熵合金的研究促进了高熵合金的工业化发展。概述了共晶高熵合金的国内外研究进展,首先详细介绍了典型共晶高熵合金AlCoCrFeNi_(2.1)的研究现状,如该合金的组织结构特征、力学性能特征及冷热加工变形行为及其变形机制。随后概括了其他共晶高熵合金系的相组成、共晶组织形貌特征及稳定性、性能等方面的研究。随后,概述了共晶高熵合金设计的方法和研究进展,主要包括基于二元合金相图与相图模拟计算的合金设计、基于多元合金混合焓的合金的设计、伪二元合金设计和基于已研究共晶高熵合金无Co元素低成本高性能共晶高熵合金的设计4个方面。最后对未来共晶高熵合金的主要研究方向做了展望。
High entropy alloys with the characteristics of high mixing entropy,sluggish diffusion and serious lattice distortion had simple structure and excellent comprehensive properties,which provided a new and wide idea for developing novel alloys.Eutectic high entropy alloys had some advantages of good fluidity,uniform compositions for the solidified structure,less casting defects and adjustable microstructure and could be used to prepared large size industry ingot,which promoted the industrial development of high entropy alloy.This review focused on the recent development of the eutectic high entropy alloy.The microstructure,mechanical properties and the behavior and mechanism of the cold and hot working deformation of AlCoCrFeNi_(2.1) eutectic high entropy alloy were summarized.AlCoCrFeNi_(2.1) eutectic high entropy alloy exhibited the typical lamellar eutectic microstructure and was composed of fcc phase and B2 eutectic phases,in which existed nanometer precipitated phases.However,the formation mechanism of the nano-precipitated phases needed to be further elucidated.The tensile fracture strength and the elongation ratio was 1.2 GPa and 22.8%.While this alloy had low elastic limit,which was not be explained with the reasonable mechanism.At-196℃,this alloy exhibited high yield strength and fracture strength of 857 and 1467 MPa,and the elongation ratios was 17%~20%.The good plasticity might be attributed into the transformation of the L12 phase into disordered solid solution phase during the low temperature deformation.During the high temperature tensile deformation,the strengthening mechanism of B2 nano-precipitated phase and the L12 nano-precipitated phase was Orowan bypass mechanism and dislocation cutting mechanism.In addition,the friction stirring process was used to adjust the microstructure.The as-cast lamellar structure transformed in the fine equiaxial structure,leading to the increase and the improvement of the strength and the plasticity.The phase constitutes,characteristics of eutectic structure and their stability,and the properties were introduced.All reported eutectic high entropy alloys were composed of two eutectic phases and exhibited unique eutectic morphology such as the eutectic-dendritic microstructure which were different from the traditional alloys.Thus,the solidification mechanism needed to be further investigated.Due to the sluggish diffusion effect,the phase and microstructure of the eutectic high entropy alloys had high thermal stability.And most reported eutectic high entropy alloys exhibited good strength and the plasticity.Besides,the eutectic high entropy alloys also possessed the excellent physical and chemical properties.For example,CoFeNi2 V0.5 Nb0.75 eutectic high entropy alloy had the good soft magnetic property,which had wide application in electrical and electronic equipment.The methods and the recent development of designing eutectic high entropy alloys were reviewed from four aspects.The first method was based on phase diagram and phase diagram simulation,in which CoCrFeNi was deemed as one element of the pseudo binary eutectic alloys.The other element of the pseudo binary eutectic alloys was selected according to the binary alloys diagrams,which could have eutectic reaction with the elements of Co,Cr,Fe and Ni.The second method was based on the mixing enthalpy of multiple-elements alloys,in which the eutectic high entropy alloy AlCoCrFeNi2.1 was selected as the reference.The elements such as Zr,Nb,Hf which had more negative binary alloy mixing enthalpy with Ni element was selected to replace Al element.The addition content of the selected elements could depend on the ratio of the mixing enthalpy of the selected element and Al element with Ni element.To design the eutectic high entropy alloys which were composed of fcc solid solution phase and the intermetallic phase,the third method was proposed which was based on the mixing enthalpy and the valence electrons.The fourth method was based on the studied eutectic high entropy alloys without Co element,low cost and excellent properties.The investigation showed that the effect of Co element on the phase and microstructure was very small.Although various methods had been proposed for designing the high entropy alloys with the eutectic compositions,there was no method for designing the alloy with the comprehensive properties,which was very interesting research direction.In the end,this review summarized the limitations of eutectic high entropy alloys at present stage as well as the prospect of its future development.The high entropy alloys provided one novel idea for designing new alloy system,which were mainly composed of solid solution phase.One of the main strengthening mechanisms was solid solution strengthening,while this was different from the mechanism in the traditional alloys.Thus,it needed to be further investigated.The proposition of eutectic high entropy alloys set a big step forward for the industrial application of high entropy alloys.However,the number of the eutectic high entropy alloys was still less.More eutectic high entropy alloys with comprehensive properties needed to be explored.And how to improve the microstructure of the as-cast high entropy alloys was one of the future research directions.
作者
郭娜娜
高绪杰
李肖逸
朱光明
赵而团
殷凤仕
Guo Nana;Gao Xujie;Li Xiaoyi;Zhu Guangming;Zhao Ertuan;Yin Fengshi(College of Mechanical Engineering,Shandong University of Technology,Zibo 255000,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2021年第6期728-739,共12页
Chinese Journal of Rare Metals
基金
山东省自然科学基金项目(ZR2017BEM003,ZR2017EMM036)
中国博士后科学基金项目(2018M632695)资助。
