Ni基高温合金单晶裂尖位错行为的动态研究——Ⅰ.DFZ 的形成及微裂纹的扩展

AN IN SITU STUDY ON DISLOCATION BEHAVIOUR OF THE CRACK TIP IN A SINGLE CRYSTAL Ni-BASE SUPERALLOY——Ⅰ.The Formation of DFZ and the Extention of Micro Crack

用透射电镜原位观察方法对 Ni 基高温合金单晶裂纹尖端位错行为进行了研究。发现在裂纹扩展的同时伴随着位错的发射,并在裂纹尖端形成无位错区(DFZ)。γ/γ′界面的存在阻碍位错的运动,并使DFZ 变短。

A series of experimental results reveal that the dislocations that emitted fromthe crack tip have a strong interaction with the γ/γ′interface in front of the crack tip.Thelength of the DFZ has been found to increase with the increase in the distance between the cracktip and the interface.The relationship may be expressed by a following equation:L(DFZ)=0.7·X_(ob)^(1.07)Taking the effect of the interfacle as a obstacle to dislocation motion into consideration,thefracture mode of DFZ proposed by Ohr should be extended to involve the effect of the interface.The result calculated is given by(?)