Methods and mechanisms for uniformly refining deformed mixed and coarse grains inside a solution-treated Ni-based superalloy by two-stage heat treatment  

作　　者：Guan-Qiang Wang Ming-Song Chen Hong-Bin Li Y.C.Lin Wei-Dong Zeng Yan-Yong Ma 

机构地区：[1]School of Mechanical and Electrical Engineering,Central South University,Changsha 410083,China [2]Light Alloy Research Institute,Central South University,Changsha 410083,China [3]State Key Laboratory of High Performance Complex Manufacturing,Changsha 410083,China [4]College of Metallurgies and Energy,North China University Science and Technology,Tangshan 063009,China

出　　处：《Journal of Materials Science & Technology》2021年第18期47-57,共11页材料科学技术（英文版）

基　　金：the National Natural Science Foundation of China(No.51975593);the Hunan Provincial Natural Science Foundation of China(No.2020JJ4113);the Science and Technology Innovation Planning Project of Hunan Province(No.2019XK2301)。

摘　　要：The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment Ni-based superalloy during two-stage annealing treatment have been investigated.The two-stage heat treatment experiments include an aging annealing treatment(AT)and a subsequent recrystallization annealing treatment(RT).The object of AT is to precipitate someδphases and consume part of storage energy to inhibit the grain growth during RT,while the RT is to refine mixed and coarse grains by recrystallization.It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high,while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low.In addition,the mixed microstructure composed of some abnormal coarse recrystallization grains(ACRGs)and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT temperature is 980℃.The phenomenon attributes to the uneven distribution ofδphase resulted from the heterogeneous deformation energy when the AT time is too short.In the regions with a large number ofδphases,the recrystallization nucleation rate is promoted and the growth of grains is limited,which results in fine grains.However,in the regions with fewδphases,the recrystallization grains around grain boundaries can easily grow up,and the new recrystallization nucleus is difficult to form inside grain,which leads to ACRGs.Thus,in order to obtain uniform and fine annealed microstructure,it is a prerequisite to precipitate even-distributedδphase by choosing a suitable AT time,such as 12 h.Moreover,a relative high RT temperature is also needed to promote the recrystallization nucleation aroundδphase.The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as:900℃×12 h+990℃×(40-60 min)and 900℃×12 h+1000℃×(10-15 min).

关 键 词：Ni-based superalloy Aging annealing Recrystallization annealing Grain refinement Microstructural evolution Mixed grain microstructure 

分 类 号：TG156[金属学及工艺—热处理]