The fracture surfaces of DZ4 specimens after rotary bending high-cycle fatigue testing with or without
shop peening were analyzed. The results show that at room temperature or 820℃,as for the specimens without shot
peening,fatigue cracks initiated from the surface or the casting defects or carbides connected to the surface. Under the
condition of Kt =1, the fracture surfaces present point source feature,and glide planes and steps can be easily seen at
these regions. With the increase of stress concentration(Kt =2, Kt =3),linear source and poly-source feature becomes
more obvious,and the glide planes become smaller and even diminish. With the rise of temperature,the glide feature of
the source regions becomes more obvious. With shot peening,the fatigue cracks initiate from inner regions, subsurface
or cast defects. As for the notched specimens,the number of the crack sources and the area of the source regions decrease,
and main cracks can be distinguished from secondary cracks. It can be thus concluded that shot peening can
improve the surface integrality of DZ4 superalloy and decrease the sensitivity of DZ4 to notches, and thus restrain the
initiation of fatigue cracks and enhance the room-temperature properties of DZ4. With the rise of temperature,the reinforcing
effect of shot peening on DZ4 decreases,but at 820℃,the reinforcing effect of shot peening still exists.