Stress-assisted discontinuous grain growth and its effect on the deformation behavior of nanocrystalline aluminum thin films

Anomalous Fatigue Behavior and Fatigue-Induced Grain Growth in Nanocrystalline Nickel Alloys

“…[26,27] Perhaps the explanation for the lack of dramatic improvements in fatigue performance is related to the instability of NC grain structures, which are known to evolve even during storage at room temperature. [28] Previous experimental observations of NC grain growth during plastic deformation, [29,30] indentation experiments [31] and as a result of fatigue loading [14,32] warrant serious consideration. The grain growth reported by Witney et al's [14] fatigue experiments on NC Cu presumably refers to modest overall grain growth, rather than discontinuous local coarsening observed in monotonic loading experiments by Gianola et al [29] In addition, several numerical models predicted evolution in NC grain structures under both elastic [33,34] and plastic [35][36][37] deformation.…”

“…[28] Previous experimental observations of NC grain growth during plastic deformation, [29,30] indentation experiments [31] and as a result of fatigue loading [14,32] warrant serious consideration. The grain growth reported by Witney et al's [14] fatigue experiments on NC Cu presumably refers to modest overall grain growth, rather than discontinuous local coarsening observed in monotonic loading experiments by Gianola et al [29] In addition, several numerical models predicted evolution in NC grain structures under both elastic [33,34] and plastic [35][36][37] deformation. These previous observations on room-temperature mechanically driven grain growth lead one to suspect that NC metals may evolve such coarse grain structures during fatigue loading, and that the fatigue mechanisms may be influenced more by the evolved grain structure than by the initial structure.…”

Microstructural evolutions and stability of gradient nano-grained copper under tensile tests and subsequent storage

“…Deformation-induced GB migration and associated grain coarsening have been experimentally verified to dominate the plastic deformation of various NG systems [10,15,18]. However, the understanding of detailed underlying mechanism is still far from mature.…”

“…The thermodynamic stabilization is achieved by reducing the driving force for grain coarsening through reducing the GB energy via GB segregation [6]. Grain coarsening induced by mechanical deformation at RT has been reported in plenty of NG samples under diverse deformation modes such as indentation [3,7], rolling [8], compression [9] and tensile loading [10]. Specifically, Zhang et al [3] reported a significant grain coarsening in NG Cu (10-100 nm) after indentation at both RT and liquid-nitrogen temperature.…”

Enhancing dislocation emission in nanocrystalline materials through shear-coupled migration of grain boundaries

“…The brittle behavior of NC materials is attributed to the suppression of conventional dislocation slips, which are dominating in their coarse-grained counterparts, as the grain size is reduced to nanoscale [1][2][3][4][5][6][7]. Meanwhile, various NC specimens that possessed both high strength and ductility have been reported [8][9][10][11][12][13][14][15][16][17][18][19]; moreover, it has been proposed that the outstanding balance was due to some grain boundaries (GBs)-mediated deformation mechanisms, such as GB sliding, emission of dislocations from GBs and GB migration [16][17][18][19][20]. Furthermore, enormous dislocation activities were discovered in the grain interiors of some NC samples in experiments [10,[21][22][23] and the accumulation of such dislocations in the grain interior due to the formation of Lomer-Cottrell locks [22] led to their exceptional strain hardening and ductility.…”