On the intrinsic ductility of electrodeposited nanocrystalline metals

Strategy for Electrodeposition of Highly Ductile Bulk Nanocrystalline Metals with a Face-Centered Cubic Structure

“…encing tensile ductility Erb and co-workers 6,22) conducted detailed investigations of the effect of specimen size on tensile ductility of electrodeposited nanocrystalline Ni and Ni alloys. These reports indicated that a specimen thickness of at least 1 mm is required to evaluate intrinsic ductility.…”

“…Despite these problems some recent studies show that good tensile ductility, around 5 10%, combined with a high strength, can be realized in electrodeposited nanocrystalline metals. 68,22) An investigation of the effect of thickness on ductility, answered the problem identified by Ma: 19) bulk specimens with thickness greater than a millimeter are required to evaluate intrinsic ductility. 22) However, there remains no solution to the problems identified by Koch et al, 20,21) in terms of achieving electrodeposited artifact-free bulk nanocrystalline metals which have high tensile ductility.…”

Failure mechanisms in metal/metal hybrid nanocrystalline microtruss materials

“…This could be achieved by modifying the grain size distribution within the electrodeposited sleeves. For example, fine-grained nanocrystalline Ni deposits (having average grain sizes in the range 10-30 nm) typically result in yield strengths of 800-950 MPa with tensile elongations to fracture on the order of $5% [31]. On the other hand, a much broader grain size distribution (e.g.…”

“…On the other hand, a much broader grain size distribution (e.g. of $20-200 nm with average of $70 nm) increases the tensile elongation to the range of 15-20% for a comparatively small reduction in yield strength ($700 MPa) [31,32]. The issues of coating adhesion and sleeve ductility will be important considerations in the development of hybrid nanocrystalline microtruss cellular materials.…”

Emergence of localized plasticity and failure through shear banding during microcompression of a nanocrystalline alloy

“…For example, nanocrystalline Cu [31] and Ni-Fe [30] showed increased strain-to-failure with improved processing chemistry that reduced particulate contamination and hydrogen pitting. Brooks et al [26] also showed that nanocrystalline Ni samples produced by an optimized process experienced twice as much plastic strain before failure, while the samples without this optimization always failed at large void-like defects produced when hydrogen gas was trapped in the deposit. Therefore, without having a proper geometry for mechanical testing and samples that are free of processing defects, conventional testing methods cannot provide us with accurate results and an alternative uniaxial testing technique is needed to adequately probe the plastic flow and failure response of nanocrystalline materials.…”