镍基单晶高温合金中的位错及其对蠕变行为的影响

Nickel-based single crystal superalloy is an extremely important high-temperature structural material, mainly used to manufacture the hot end components such as aero-engine blades. Dislocations are the main reason for plasticdeformation of materials and can directly lead parts to failure or fracture. The dislocations in nickel-based single crystal superalloys formed in actual service processes, come in many types and morphologies and have different effects on creep performance. Therefore, the research on the relationship between dislocation and creep mechanism has been the focus of superalloys performance research, and has attracted the attention of researchers at home and abroad. The single crystal sueralloys consists of γ matrix and γ' precipitate. The dislocations in Ni-based single crystal superalloys mainly include: independent dislocations in γ matrix, stacking fault, dislocation network, and super dislocations in γ' precipitate, which are the result of interactions between dislocations and solute atoms, dislocations and γ' precipitate, and dislocations and dislocations. Independent dislocations are formed in matrix channel at primary creep and are the source of all dislocations such as dislocation network and super dislocations. Stacking fault is the most common dislocation configuration in low temperature creep of superalloys. It can exist alone in the γ matrix phase, as well as in the γ' phase. The stacking fault morphology is related to the fault energy of γ and γ' phase. The interface dislocation network is mainly tetragonal or hexagonal, and is concentrated in the vicinity of the γ/γ' two phase interface, which is one of the typical structural features of high temperature creep. There are two kinds of super dislocations entering γ' precipitate under high temperature creep, which are <110> type super dislocation and <010> type super dislocation. The mechanisms of the two super dislocations through γ' phase are obviously different. <110> type super dislocations mainly pass through the γ' phase in a cutting manner, while <010> type super dislocations can only pass through the γ' phase by a slipping and climbing combination manner. Dislocations determine the properties of superalloys. Stacking fault is the performance of lowfault energy of alloys. Low stacking fault energy will increase primary creep and shorten creep life of low temperature creep of the alloys. The interface dislocation network is the result of interaction between dislocations and two-phase misfit stress, which hinders subsequent dislocation cutting through γ' phase. It is very beneficial to improve the high temperature creep performance of superalloys. Dislocation through γ' phase is considered to be the controlling factor for high temperature creep of superalloys. The type of the super dislocation entering the γ' phase is different, and the creep properties are also significantly different. The understanding of dislocation morphology, structure, and formation processes in superalloys is the basis study of creep mechanism for superalloys. The analysis of the dislocation type influence on creep performance and the influencing factors of dislocation formation can provide new ideas for alloy design. In this paper, several typical dislocations in nickel-based single crystal superalloys are reviewed from three aspects: dislocation morphology and structure, dislocation formation mechanism, and the influence of dislocations on creep properties. The morphological characteristics of different types of dislocations are clarified, and the internal mechanism of dislocationinfluence creep properties is analyzed. The general laws of alloying element strengthening are summarized. On this basis, several potential technical approaches to improve the creep properties of single crystal superalloys are proposed.