FCC/L12共格高熵高温合金的研究进展

A Review on High-entropy Superalloys with FCC/L12 Structure

高温合金是航空航天、能源等领域的高端装备核心热部件的关键材料。多年来,研究人员通过微合金化和先进制造工艺等方法,不断提升传统高温合金的性能,但由于受到合金主元的熔点限制,当前先进高温合金的性能已接近其极限。自2004年以来,高熵合金作为一种新型的合金体系表现出优异的综合性能,得到了广泛关注。高熵合金包含多种主元,在性能上的鸡尾酒效应可以融合各个主元的特点,突破了单一主元对合金性能的限制。随着对材料性能需求的不断提高,高熵合金也不仅限于单相固溶体,近年来也开发了大量第二相强化的高熵合金。其中,高熵高温合金结合了高熵合金多主元设计思想和传统高温合金共格析出的结构特点,表现出稳定的FCC/L12相结构和优异的高温性能,为新型高温结构材料的开发提供了希望。然而,高熵高温合金的相形成规律缺乏可靠的理论,强化和变形机理缺乏系统研究。此外,高温材料在环境中的表面稳定性是在工程应用中衡量材料性能的重要指标,而相关研究较少。近年来,研究人员基于已有的合金设计经验和计算机模拟方法,开发了一系列高熵高温合金,通过添加多种合金化元素不断提高材料的高温性能,研究了L12相的析出形貌和热稳定性、FCC/L12间的晶格错配度等对高温强度、蠕变性能的影响,并且对一些综合性能优异的高熵高温合金进行了高温氧化和热腐蚀测试,推进了高温高熵合金的工业化应用。本文归纳了高熵高温合金的研究进展,分别对相形成规律、力学性能、高温氧化和热腐蚀等进行了简单介绍,分析了变形机制、氧化和热腐蚀机理,指明了未来高熵高温合金的发展方向,以期为高熵高温合金的研发和工程应用提供一定的参考。

Superalloys are unique high-temperature materials widely used in the aerospace and energy industry.The performance of conventional supe-ralloys has been improved by alloying and advanced manufacturing processes during the past decades.However,operating temperatures are now reaching limits posed by the melting temperatures of these materials.Since 2004,a new alloy design and development philosophy—high-entropy alloys(HEAs),or multi-principle-element alloys(MPEAs)—has attracted significant attention.The four core effects of HEAs,including high configurational entropy,sluggish diffusion,severe lattice distortion,and cock-tail effect,are mainly responsible for the various physical and mechanical properties.To develop higher performance of HEAs,precipitation strengthening has been widely applied in HEAs and is proved to be effective in strengthening or toughening.Based on the HEA concept and the coherent microstructure of FCC/L12,a series of high-entropy superalloys(HESAs)has been developed with high strength and long-time microstructural stabilities at high temperatures.However,the work about phase formation of HESAs were few,and the mechanisms of strengthening and deformation still lacked systematic research.In addition,the surface stability of materials at elevated temperature is an important indicator in engineering applications,but there were few studies.Recently,researchers have developed a series of HESAs based on the empirical phase formation rules and computer simulation methods.The effects of morphology and stability for the L12 precipitated phase,the lattice mismatch,etc.on high-temperature performance,such as high strength and creep property were studied.Moreover,the surface stability of some HESAs were investigated in oxidizing and corrosive environments.The present work summarizes the research progress of HESAs.The phase formation,mechanical properties,high temperature oxidation and corrosion are briefly reviewed.Finally,the future perspective of HESAs is prospected.