In-situ synchrotron high energy X-ray diffraction study on the internal strain evolution of D019-α2 phase during high-temperature compression and subsequent annealing in a TiAl alloy  

作　　者：X.Liu L.Song A.Stark F.Pyczak T.B.Zhang 

机构地区：[1]State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072,China [2]Innovation Center NPU Chongqing,Northwestern Polytechnical University,Chongqing 400000,China [3]Institute of Materials Physics,Helmholtz-Zentrum Hereon,Max Planck-Str.1,Geesthacht 21502,Germany

出　　处：《Journal of Materials Science & Technology》2023年第32期212-222,共11页材料科学技术（英文版）

基　　金：the National Natural Science Foundation of China(No.51971175);Natural Science Foundation of Shanghai(No.22ZR1467400);Chongqing(No.CSTB2022NSCQMSX1113);the“111”Project(No.B20028).

摘　　要：The residual stress in the D019-α2 phase is known to be significantly higher than that in the L10-γphase in TiAl alloys after deformation due to the poor plasticity and strong mechanical anisotropy of theα2 phase.However,the internal stress accumulation and relaxation in theα2 phase during high-temperature deformation and annealing are scarcely investigated.In this study,for the first time,the internal strain evolution and load partitioning between theα2 andγphases at high temperatures are characterized by in-situ synchrotron high energy X-ray diffraction(HEXRD)technique.The plastic deformation is at least initiated at a stress of roughly 200 MPa in theγphase and 775 MPa in theα2 phase.The intergranular strains in theα2 phase are generated by the onset of dislocation glide in theγphase,and accentuated with the accumulated dislocations and the ensuing twinning activity.After unloading,great intergranular strains are preserved in theα2 phase constrained by the heavily plastically deformedγphase.During subsequent heating from 400 to 1000℃,the internal strains in theα2 phase are almost fully relaxed by substantial dislocation annihilation and rearrangement in theγphase.During annealing at 800℃,the internal strain relaxation is rapid in the initial 10 min,whereas considerably retarded subsequently.The extent of relaxation after holding at 800℃for 1 h is equivalent to that of heating in an effective temperature range of 680-880℃for 10 min.The in-situ lattice strain measurements with various thermal relaxation schemes provide guidance for the stress relief annealing of TiAl components.

关 键 词：TiAl alloys Synchrotron radiation Intergranular strain Stress relaxation 

分 类 号：TG146.23[一般工业技术—材料科学与工程]