摘要
镍基高温合金具有优良的成分兼容性、良好的组织稳定性、抗氧化和抗腐蚀性能,被广泛用于航空发动机和地面燃气轮机的涡轮叶片等关键的热端部件。沉淀相γ′对位错运动的阻碍是镍基高温合金的主要强化作用之一。一般而言,这种阻碍作用不仅与γ′相的形貌、体积分数及尺寸有关,也取决于γ′相与位错的交互作用。通常这种交互作用机制可分为三种:切割机制、Orowan绕过机制和热激活攀移机制。当不同类型的位错切割γ′相时,在γ′相中会形成不同的高能缺陷,能够阻碍位错运动,延缓材料软化。这类结构或成分缺陷包括:反相畴界(APB)、复杂层错(CSF)、超点阵内禀层错(SISF)、超点阵外禀层错(SESF)和微孪晶。微孪晶化(Micro-twinning)是镍基高温合金中一种重要的变形机制,主要发生在中温高应力条件下。此外,中温拉伸变形过程中也有微孪晶产生。早期研究表明,微孪晶的产生与SESF有关,可以认为SESF是“胚体孪晶”,且SESF是由a/3〈112〉超点阵不全位错切入γ′相产生的。基于溶质原子短程扩散的原子重排(Reordering)机制被用来解释微孪晶的形成,即a/6〈112〉不全位错切入γ′相中先产生CSF,而后CSF通过原子重排转变为SESF,最终形成微孪晶。最近的研究表明,在微孪晶产生过程中,Co和Cr原子会在成分偏析和柯氏气团的作用下发生长程扩散,因此有学者指出微孪晶的形成是原子重排短程扩散机制和偏析主导的长程扩散共同作用的结果。同时,对于高温合金微孪晶机制的研究,研究人员不再局限于其形成机制,而对微孪晶的长大机制有了进一步的理解。共格的纳米孪晶界作为金属材料中的一种特殊缺陷,可以有效阻碍位错运动,从而强化材料,这种强化方式已经在纳米铜、TWIP钢以及TiAl合金中得到应用。研究人员发现,孪晶能够强化固溶强化的镍合金;同时,有学者�
Ni-based single crystal superalloys have long been the candidate materials for applications in the critical components of the gas turbine engines due to their superior composition compatibility,microstructural stability,and creep,fatigue,oxidation,corrosion resistances.The inhibition of dislocation motion byγ′precipitates is one of the main strengthening effects of nickel-based superalloys.In general,this hindrance is related not only to the morphology,volume fraction and size ofγ′precipitates,but also to the interaction ofγ′precipitates and dislocation.Usually this inte-raction mechanism can be divided into three types:shearing mechanism,Orowan looping mechanism and thermal activation climbing mechanism.When different types of dislocations cut theγ′phase,different high-energy defects are formed in theγ′phase,which can hinder creep and fatigue.Examples of these structural and chemical defects include antiphase boundaries(APB),complex stacking faults(CSF),superlattice intrinsic stacking faults(SISF),superlattice extrinsic stacking faults(SESF)and micro-twins.Micro-twinning is an important deformation mechanism in nickel-based superalloys.It mainly occurs under medium-temperature and high-stress conditions.In addition,during the mid-temperature tensile deformation,micro twinning occurs.Early studies have shown that the appearance of micro-twins is related to the superlattice extrinsic stacking faults(SESF),which is produced by a/3〈112〉superlattice partial dislocations and can be considered as“embryonic twin”.Subsequently,the reordering mechanism based on the short-range diffusion of solute atoms is used to explain the formation of micro-twins.Firstly,the a/6〈112〉partial dislocation cut into theγ′phase to produce complex stacking faults(CSF),and then the complex stacking faults are transformed to SESF by atomic rearrangement.Finally,micro-twins are eventually formed.Recent studies have shown that in the process of micro-twinning,the long-range diffusion of critical elements such as Cr a
作者
屈鹏飞
杨文超
岳全召
曹凯莉
刘林
QU Pengfei;YANG Wenchao;YUE Quanzhao;CAO Kaili;LIU Lin(State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2019年第23期3971-3978,共8页
Materials Reports
基金
国家自然科学基金(51771148
51631008
51690163)
陕西省自然科学基础研究计划(2019JM-319)
中央高校基本科研基金(3102018JCC009
3102019PB001)~~
关键词
镍基高温合金
变形机制
微孪晶
元素偏析
孪晶强化
nickel-based superalloy
deformation mechanism
micro-twins
element segregation
twin strengthening
