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.H...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.展开更多
基金the National Natural Science Foundation of China(No.51971175)Natural Science Foundation of Shanghai(No.22ZR1467400)+1 种基金Chongqing(No.CSTB2022NSCQMSX1113)the“111”Project(No.B20028).
文摘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.
