The experimental evidence for the Hall-Petch dependence of strength on the inverse square-root of grain size is reviewed critically. Both the classic data and more recent results are considered. While the data are traditionally fitted to the inverse square-root dependence, they also fit well to many other functions, both power law and non-power law. There have been difficulties, recognized for ...

Abstract Microstructural characterisation of engineering materials is required for understanding the relationships between microstructure and mechanical properties. Conventionally grain size measured from boundary maps obtained using optical or electron microscopy. This paper implements EBSD-based linear intercept measurement spatial variation ferritic steel weld metals, making analysis flexibl...

Ultrafine-grained (UFG) nanostructured materials having grain sizes of tens and hundreds of nanometers recently have aroused interest among researchers in the materials science field. With respect to their mechanical properties, one would hope to be able to obtain the extremely strong states that can be expected in the case of strong grain refinement according to the Hall-Petch relationship (Gl...

Nanotwinned metals exhibit an unusual combination of ultrahigh strength, considerable ductility and enhanced rate sensitivity. We find that a Hall–Petch-type relationship closely fits the experiment data of activation volume as a function of twin spacing. The results suggest a transition of the rate-controlling mechanism from intra-twinto twin-boundary-mediated processes with decreasing twin la...

We have conducted highP-Tsynchrotron X-ray and time-of-flight neutron diffraction experiments as well as indentation measurements to study equation of state, constitutive properties, and hardness of nanocrystalline and bulk nickel. Our lattice volume-pressure data present a clear evidence of elastic softening in nanocrystalline Ni as compared with the bulk nickel. We show that the enhanced over...

Very fine-grained Ni and Cu films were formed using pulsed laser deposition on fised silica substrates. The grain sizes in the films were characterized by electron microscopy, and the mechanical properties were determined by ultra-low load indentation, with iinite-element modeling used to separate the properties of the layers from those of the substrate. Some Ni films were also examined after a...

Deformation Behaviour of microcrystalline (mc) and nanocrystalline (nc) Mg-5%Al alloys produced by hot extrusion of ball-milled powders were investigated using instrumented indentation tests. The hardness values of the mc and nc metals exhibited indentation size effect (ISE), with nc alloys showing weaker ISE. The highly localized dislocation activities resulted in a small activation volume, he...