Hall–Petch description of nanopolycrystalline Cu, Ni and Al strength levels and strain rate sensitivities

Strength and strain rate sensitivity measurements for nanopolycrystalline copper, nickel and aluminium materials are assessed on the basis of a Hall–Petch method of analysis. The H–P kε values are attributed to the need for cross-slip in the grain boundary regions. Transition of the H–P dependence to the stress for a single dislocation loop expanding against the grain boundary resistance provides an explanation of higher measurements for nanoscale aluminium material.