INTERFACIAL EFFECTS OF FATIGUE CRACKING IN METALLIC MATERIALS
金属材料疲劳损伤的界面效应

Interfacial fatigue cracking behaviors along large--angle grain boundaries (GBs), twin boundaries (TBs), phase boundaries (PBs) and joint interfaces in metallic materials were summarized. It is found that the resistance to fatigue crack initiation decreases in the order of low--angle GBs, persistent slip bands and the large--angle GBs in pure Cu. For annealing TBs, fatigue cracking initiation strongly depends on the stacking fault energy (SFE) in Cu alloys. With decreasing SFE, fatigue cracking along TBs becomes easy. In Cu--Ag binary alloys, the misorientation across GBs or PBs plays an important role in the fatigue cracking, and large misorientation often makes the final fatigue cracking. For the Cu/solder joint interface, the interfacial fatigue cracking modes are affected by the solders and aging time. In Sn--Ag/Cu solder joints, fatigue crack normally nucleates along the interface between the Sn--Ag solder and the intermetallics compounds (IMCs); however, for Sn--Bi/Cu solder joints, brittle interfacial fatigue cracking always occurs along the interface between Cu and the IMCs due to the Bi segregation after aging for a long time.