title: The Hall-Petch effect as a manifestation of the general size effect.
abstract: 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 half-a-century, in the inverse square-root expression. It is now explained as an artefact of faulty data analysis. A Bayesian meta-analysis shows that the data strongly support the simple inverse or lnd/dexpressions. Since these expressions derive from underlying theory, they are also more readily explicable. It is concluded that the Hall-Petch effect is not to be explained by the variety of theories found in the literature, but is a manifestation of, or to be underlain by the general size effect observed throughout micromechanics, owing to the inverse relationship between the stress required and the space available for dislocation sources to operate.
authors.affiliation: School of Physics and Astronomy , Queen Mary University of London , London E1 4NS, UK.
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Engineering and Materials Science, Queen Mary University of London , London E1 4NS, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Bushby
authors.affiliation: School of Physics and Astronomy , Queen Mary University of London , London E1 4NS, UK.
authors.forename: D J
authors.identifier: 0000-0003-0725-1841
authors.initials: DJ
authors.lastname: Dunstan
keywords: Hall–Petch equation; dislocations; elastic–plastic material; grain boundaries; probability and statistics