Abstract
Traditional nanostructured metals are inherently comprised of a high density of high-energy interfaces that make this class of materials not stable in extreme conditions. Therefore, high performance bulk nanostructured metals containing stable interfaces are highly desirable for extreme environments applications. Here, we reported an attractive bulk Cu/V nanolamellar composite that was successfully developed by integrating interface engineering and severe plastic deformation techniques. The layered morphology and ordered Cu/V interfaces remained stable with respect to continued rolling (total strain exceeding 12). Most importantly, for layer thickness of 25 nm, this bulk Cu/V nanocomposite simultaneously achieves high strength (hardness of 3.68 GPa) and outstanding thermal stability (up to 700 °C), which are quite difficult to realize simultaneously in traditional nanostructured materials. Such extraordinary property in our Cu/V nanocomposite is achieved via an extreme rolling process that creates extremely high density of stable Cu/V heterophase interfaces and low density of unstable grain boundaries. In addition, high temperature annealing result illustrates that Rayleigh instability is the dominant mechanism driving the onset of thermal instability after exposure to 800 °C.
Highlights
Bulk nanolamellar composites with controllable average individual layer thicknesses
In our previous work[33], we reported that cross accumulative roll bonding (CARB) combined with an intermediate annealing process can effectively minimize plastic instabilities and the formation of edge cracks, and this technique was successfully exploited to prepare high performance bulk Cu/Ta multilayer composite sheets with a minimum individual layer thickness of 50 nm
As reported previously[33], at a certain total strain, in contrast to the sample prepared via the ARB process, where the strain incompatibility accumulate in a single rolling-normal direction (RD–ND) section, which significantly promoted the formation of shear bands, the CARB process could effectively lower the strain incompatibility by distributing the strain evenly in the rolling direction (RD) and transverse direction (TD)
Summary
Bulk nanolamellar composites with controllable average individual layer thicknesses. Recent investigations on ARB-fabricated nanolayered sheets mainly focused on the Cu/Nb system and this ARB Cu/Nb composite, like the nanolayered composite films produced by PVD, possesses continuously layered, fine-scale micro-structures and excellent resistance to extreme conditions[10,22,23,24,25,26]. In our previous work[33], we reported that cross accumulative roll bonding (CARB) combined with an intermediate annealing process can effectively minimize plastic instabilities and the formation of edge cracks, and this technique was successfully exploited to prepare high performance bulk Cu/Ta multilayer composite sheets with a minimum individual layer thickness of 50 nm. On this basis, interface-dominant bulk Cu/V nanolamellar composite sheets were developed for the first time via CARB in this study.
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