Systematic analysis of distinct flow characteristics and underlying microstructural evolution mechanisms of a novel fine-grained P/M nickel-based superalloy during isothermal compression  

作　　者：Hongning Wen Junsong Jin Xuefeng Tang Xinyun Wang Heyang Yang Yiding Zhang Lei Deng Pan Gong Qingsong Wei Yingjie He Jianzheng Guo 

机构地区：[1]State Key Laboratory of Materials Processing and Die&Mould Technology,School of Materials Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,China [2]Shenzhen Wedge Central South Research Institute Co.,Ltd.,Shenzhen 518000,China [3]State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China

出　　处：《Journal of Materials Science & Technology》2023年第31期57-73,共17页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foundation of China(Nos.52175319 and 52090043);the Fundamental Research Funds for the Central Universities(No.YCJJ202202003);the National Science and Technology Major Project(No.2017-Ⅵ-0009-0080).

摘　　要：Isothermal forging(IF)is an effective method for forming difficult-to-deform materials like P/M superalloys.Understanding the isothermal compression microstructural evolution mechanism of a novel P/M s-peralloy provides the basis for its optimized IF planning.In this study,the isothermal compression tests of a novel fine-grained P/M nickel-based superalloy were carried out at 1000-1150℃with strain rates of 0.001-0.01 s^(−1).The results indicated that the alloy exhibits three distinct flow characteristics:continuous softening after reaching the peak stress,near-steady superplastic flow,and discontinuous hardening,corresponding to different strain rate sensitivity exponent(m)values.Varied microstructural evolution mechanisms,including grain boundary sliding(GBS),dynamic recrystallization(DRX),and grain growth,are dominated in different m-value domains.Meanwhile,different roles of primaryγ’play in microstruc-tural evolution were clarified.A moderate fraction of primaryγ’with 8.5%-14.2%can well coordinate the GBS and hinder excessive grain growth at a high m value domain(m>0.4).When 0.2<m<0.4,the role of the primaryγ’is changed to promote dislocation accumulation,accelerating the nucleation of DRXed grains.As the primaryγ’is dissolved at 1150℃,obvious grain growth was observed after compression.Work hardening effect by overgrown grains competed with DRX softening results in the discontinuous rising stress.

关 键 词：P/M nickel-based superalloy Flow characteristic Microstructural evolution Superplastic flow Dynamic recrystallization 

分 类 号：TG132.3[一般工业技术—材料科学与工程]