Dislocation-free zones in fatigued copper polycrystals

Fatigue behaviors of AISI 316L stainless steel with a gradient nanostructured surface layer

“…The mechanisms of fatigue damage in CG fcc metals have been investigated comprehensively [49][50][51][52][53][54]. During fatigue, dislocations generate and accumulate in grains, resulting in the formation of unique dislocation structures (mostly PSB) to minimize the total free energy.…”

Evolution of Dislocation Structure and Fatigue Crack Behavior in Fe–Si Alloys during Cyclic Bending Test

“…Winter et al 17) and Luoh et al 23) reported that dislocation free zones (DFZ) along grain boundaries were formed when the vein structures developed within grains, whereas DFZ were not formed in the case of cell structures, which is very similar to the results of the present study using Fe-Si alloy. Although further study is required, Luoh et al 23) concluded that the multipolar dislocation loop patches (MLPs) and walls (MLWs) are built up due to grain boundary incompatible stresses providing secondary glides, which are thought to cause annihilation of dipole loops by intersecting MLPs or MLWs. Referring to this model, it is inferred that in the Si-bearing steels the difficulty of cross slip leads to the annihilation of dislocation dipole loops in the vicinity of grain boundaries by intersecting MLPs and MLWs, or dislocations simply sinks into grain boundaries.…”

“…Concerning the interaction between dislocations and grain boundaries during the cyclic test, detailed studies on Cu polycrystal, 17,23) Cu bicrystal 24) and Al polycrystal 25) were carried out taking into account the grain boundary characteristics. Winter et al.…”

“…2) Low dislocation-density regions were found along all of the adjacent initial grain boundaries with a distance of ap-proximately 0.5 mm in the Si-bearing steels. Concerning the interaction between dislocations and grain boundaries during the cyclic test, detailed studies on Cu polycrystal, 17,23) Cu bicrystal 24) and Al polycrystal 25) were carried out taking into account the grain boundary characteristics. Winter et al 17) and Luoh et al 23) reported that dislocation free zones (DFZ) along grain boundaries were formed when the vein structures developed within grains, whereas DFZ were not formed in the case of cell structures, which is very similar to the results of the present study using Fe-Si alloy.…”

The Study of Fatigue Behaviors and Dislocation Structures in Interstitial-Free Steel

“…At the fatigue failure stage of De/2 = 0.125 pct, the small dislocation cells tend to form near the grain boundaries than large dislocation cells; such dislocation structure gradient implies that the sustained cyclic stress for the grain interior and the region near the grain boundary are unequal. Luoh and Chang [22] and Figureoa et al [8] have indicated that the incompatibility induced by neighbor grains will cause the dislocation structures near the grain boundary and in the grain interior to be different. Hence, incompatible stress between the grains should have a significant effect on dislocation development near the regions of grain boundary.…”