单晶镍基高温合金DD8反位相热机械疲劳后的层错

STACKING FAULT IN γ PRECIPITATE OF SINGLE CRYSTAL NICKEL BASE SUPERALLOY DD8 AFTER OUT-OF-PHASE THERMO- MECHANICAL FATIGUE

对镍基单晶高温合金DDS在恒机械应变控制下的反位相(OP)热机械疲劳(TMF)实验后的微观结构进行了研究.结果表明,DD8单品经过OP TMF后γ’沉淀相被Schockley不全位错剪切,而不是象在等温疲劳(IF)那样是被位错对剪切,经过分析得出,γ’沉淀相是被位错对还是Schockley不全位错剪切,在适当的温度下,与形变的速度和施加的应力大小有很大的关系.

The microstructures of single crystal nickel base superalloy DD8 were investigated after out.-of-phase(OP) thermomechanical fatigue(TMF). It is found thatγ' precipitates are sheared by Schockley partial dislocations, which is different from the case in which γ' precipitates are sheared by (1/2)(110) dislocation pair under isothermal fatigue (IF). It is presumed that whetherγ' precipitates are sheared by Schockley partial dislocation or by dislocation pair is related to both deformation rate and stress amplitudes at the appropriate temperature.