Analysis of plastic deformation in nanoscale metallic multilayers with coherent and incoherent interfaces

Smaller critical size and enhanced strength by nano-laminated structure in nickel

“…Apparently, GB activities can be inhibited by the laminated structure at the samle length scale compared to the equiaxed grain structure, which is mainly due to the different grain structures and the defect structures at the boundaries. Moreover, according to previous research [22,43,44], dislocations can not easily move from one layer to another layer in bi-metal multilayered system in spite of continuity of slip mostly due to the in-plane internal strains and stresses. These internal strains and stresses are induced by matching of the two adjacent lattices with misfit dislocations at the interfaces, and the maximum strength for interface crossing mechanism at the critical layer thickness is highly related to the internal stresses.…”

“…These misfit dislocations at the interfaces of the laminated structure should create internal stresses at the long interfaces similar to the bi-metal multilayered system and the dependence of internal stresses on the lamellar thickness for the laminated structure should be more sensitive than the polycrystal model with randomly oriented equiaxed grains. As indicated [22,43,44], one of important effects on strengthening derives from the internal strains and stresses, which gives another reason why the laminated structures possess enhanced strength compared to the equiaxed grain structure.…”

Coherent Interfaces Increase Strain-Hardening Behavior in Tri-Component Nano-Scale Metallic Multilayer Thin Films

“…[1] The yield strength of the films is more similar between samples, with the average strength of the 5 nm layers being only slightly higher than the 30 nm layers. Since the initial yield of the composite signifies the strength required to initiate dislocation motion in the softest layer, and thus is an inherent material property, it is not surprising that the yield strength is not as strongly affected by the layered structure.…”

“…[1][2][3][4] However, the experimental validation of the strain-hardening behavior [2] has only been carried out at a single tri-layer thickness period. With significant evidence in bi-layer NMMs that layer thickness plays a substantial role in controlling the deformation processes in the confined layer slip (CLS) regime, [5][6][7] this effect of layer thickness on tri-layer systems needs to be evaluated.…”

“…With significant evidence in bi-layer NMMs that layer thickness plays a substantial role in controlling the deformation processes in the confined layer slip (CLS) regime, [5][6][7] this effect of layer thickness on tri-layer systems needs to be evaluated. Briefly, as described in [1], the presence of two adjacent FCC layers with different elastic moduli causes shear stresses to develop at the chemically distinct, but coherent, interface as a threading dislocation moves through the FCC layers. This shear stress can lead to cross-slip at higher stresses, assisted by the high strength imparted by the incoherent interface at the FCC/BCC layers.…”