Cyclic deformation induced strengthening and unusual rate sensitivity in Cu/Ru nanolayered films. (December 2017)

• Record Type: Journal Article
• Authors: Cao, Z.H.; Wei, M.Z.; Ma, Y.J.; Sun, C.; Lu, H.M.; Fan, Z.; Meng, X.K.
• Is Part Of: International journal of plasticity. Volume 99(2017:Dec.)
• Page Start: 43
• Page End: 57
• Publication Date: 2017-12
• Subjects: Layered material -- Cyclic loading -- Rate sensitivity -- Strengthening mechanisms -- Dislocations; Plasticity -- Periodicals; Plasticité -- Périodiques; Plasticity; Periodicals; 620.11233
• DOI: 10.1016/j.ijplas.2017.08.005
• Languages: English
• ISSNs: 0749-6419

Abstract

Abstract: In this work, we have systematically investigated the effect of cyclic deformation on the strength and rate sensitivity of Cu/Ru multilayers with different individual layer thickness ( h ) by nanoindentation tests. It was found that cyclic deformation remarkably enhances the hardness of Cu/Ru multilayers comparing with the specimens by monotonic loading. The rate sensitivity ( m ) of multilayer exhibits an anomalous size dependence after nanoscale cyclic deformation. When h > 10 nm, the m linearly increases with increasing cycle number of loading-unloading ( s ). However, the m sharply decreases with increasing s when h < 10 nm, presenting an inverse cyclic deformation effect on m . An obvious Bauschinger effect is observed during cyclic loading, where the evolution of effective stress is consistent with the m . Cyclic deformation induced dislocation accumulation and arrays at the heterogeneous interface are the intrinsic plastic mechanism for the enhanced rate sensitivity. The formation of amorphous layers at the critical h is mainly responsible for the inverse size m . Highlights: Cyclic deformation induced strengthening/softening in multilayers is studied by nanoindentation. Unusual rate sensitivity is found at nanoscale multilayers during cyclic loading. Size dependent Bauschinger effect is observed in multilayers during cyclic loading. Heterogeneous interface structure evolution with layer thickness is analyzed by HRTEM. Transition from dislocation accumulation to interface amorphization mechanism is revealed.