摘要
固溶体基体上析出的第二相粒子的种类、形貌(大小和形状)以及分布,对提升合金的力学性能具有决定性作用,其中第二相粒子的共格析出更有利于提升合金的高温力学性能。例如,正是由于立方形态的L12-Ni 3Al有序超结构相在FCC固溶体基体的共格析出,才使得Ni基高温合金具有优异的高温力学性能。近年来,体心立方(BCC)基多元合金中的第二相共格析出强化使得该类合金展现出优异的力学性能,尤其是优异的高温强度,引起了广泛关注。在传统的BCC基工程合金材料中,主要采用非共格和半共格析出相对合金进行强化,然而第二相粒子在时效过程中易发生粗化,使得合金脆性增加,从而导致合金对工艺异常敏感。最新研究表明,在BCC基多主元合金中,可实现有序B2(L21)相在无序BCC基体上的共格析出,有望改善BCC基合金的强韧性。目前,获得的共格组织多表现为编织网状的调幅分解组织,很难实现球形或立方形态的共格纳米粒子析出,这也会造成合金具有极大的脆性,故如何在BCC基多主元合金中获得立方形或球形的共格粒子是目前的研究热点。研究表明,基体与有序析出相间的点阵错配度是决定析出粒子形状和大小的最关键因素,故通过调节多主元合金中的元素类型及含量来调控BCC基体和有序析出相(B2/L21)的成分,以调节二者的点阵错配,可以获得期望的共格组织。如BCC基特种钢和高熵合金中,通过调控成分可以调整BCC基体与共格B2相之间的点阵错配,继而使球形/立方形的B2粒子共格析出在BCC基体上,以获得一系列性能优异的BCC基特种钢及高熵合金。本文详细总结了几种典型的BCC基多元合金(如特种钢、高熵合金等)中共格析出相粒子的形貌、分布及力学性能;讨论了点阵错配度与析出粒子形貌之间的关系;并阐述了析出强化的机制;最后对共格析出强化的BCC基多元合金的发展及应用前景进行了展望。
The type,morphology(size and shape),and distribution of the second-phase particles precipitated on the solid solution matrix are dominant on the improvement of mechanical strengths of alloys.In particular,the coherent precipitation of particles is more beneficial to enhance the high-temperature mechanical properties of alloys.For example,it is the coherent precipitation of cubic L12-Ni 3Al ordered phase in FCC solid solution matrix that renders Ni-based superalloys with excellent high-temperature mechanical properties.Recently,the body-centered-cubic(BCC)-based multi-component alloys containing coherent precipitates have attracted extensive attention due to their prominent mechanical properties(especially high strength at elevated temperatures)induced by precipitation strengthening.However,the non-coherent or half-coherent precipitated phases were often used to strengthen the matrix in conventional BCC-based enginee-ring alloys,which induces the coarsening of the second-phase precipitates during the aging period and embrittles alloys.Such alloys are generally sensitive to the post-processing.Recently,the ordered phase B2(L21)precipitation into disordered BCC matrix could be achieved in multi-principal alloy systems,which has great potential to improve the strength and toughness of alloys.The existing results show that BCC/B2 coherent microstructure exhibits a weave-like spinodal decomposition and it is difficult to precipitated the spherical or cuboidal B2/L21 nanoparticles,which also leads to a serious brittleness.Therefore,how to obtain cubic or spherical coherent particles in BCC-based multi-component alloys is a research hotspot.It has been demonstrated that the lattice mismatch between the matrix and ordered phases is the most critical factor to determine the shape and size of precipitates.Therefore,the compositions of the BCC matrix and the ordered phase can be regulated by adjusting the species and amounts of alloying elements in alloys for the achievement of an optimum lattice mismatch matching the desired coherent microstructure.For example,in BCC-based special steels and high-entropy alloys,the spherical or cuboidal B2 nanoparticles were coherently precipitated into the BCC matrix through adjusting the lattice mismatch between BCC and B2 phases,by which a series of BCC-based special steels and high-entropy alloys with excellent properties could be obtained.The present work summarizes comprehensively the phase structures and morphologies of coherent precipitates in several typical BCC-based alloys,such as special steels and high-entropy alloys.The mechanical properties of these alloys are also generalized.Then,the relationship between the lattice misfit and the particle morphology,and the mechanism of precipitation strengthening are illuminated.Finally,the development and application of coherently precipitation-strengthened BCC-based alloys are prospected.
作者
信思树
王镇华
李春玲
王清
XIN Sishu;WANG Zhenhua;LI Chunling;WANG Qing(Kunming Institute of Physics,Kunming 650000,China;Key Laboratory of Materials Modification by Laser,Ion and Electron Beams of Ministry of Education,School of Materials Science and Engineering,Dalian University of Technology,Dalian 116024,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2020年第7期130-137,共8页
Materials Reports
基金
国家自然科学基金重点联合项目(U1867201).
关键词
BCC基多元合金
共格析出
微观组织
力学性能
BCC-based multi-component alloys
coherent precipitation
microstructure
mechanical properties
