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Implications of Fatigue-Crack Healing in Nanocrystalline Metals [Slides]

Boyce, Brad B.; Barr, Christopher M.; Duong, Ta; Bufford, Daniel C.; Molkeri, A.; Heckman, Nathan H.; Adams, David L.; Hattar, Khalid M.; Demkowicz, Michael J.

Under high-cycle fatigue conditions, a fatigue crack in nanocrystalline Pt was observed to undergo healing. The healing appears to occur by cold welding, facilitated by grain boundary migration, and also by local closure stresses. The healing may help explain several observations: role of air (or vacuum) on fatigue life, impeded subsurface fatigue cracking, apparent flaw healing in sub-critical cycling of ceramics, the existence of a fatigue threshold, and the role of vacuum on the fatigue threshold.