title: Revealing the maximum strength in nanotwinned copper.
abstract: The strength of polycrystalline materials increases with decreasing grain size. Below a critical size, smaller grains might lead to softening, as suggested by atomistic simulations. The strongest size should arise at a transition in deformation mechanism from lattice dislocation activities to grain boundary-related processes. We investigated the maximum strength of nanotwinned copper samples with different twin thicknesses. We found that the strength increases with decreasing twin thickness, reaching a maximum at 15 nanometers, followed by a softening at smaller values that is accompanied by enhanced strain hardening and tensile ductility. The strongest twin thickness originates from a transition in the yielding mechanism from the slip transfer across twin boundaries to the activity of preexisting easy dislocation sources.
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P.R. China. llu@imr.ac.cn
authors.forename: L
authors.initials: L
authors.lastname: Lu
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.forename: X
authors.initials: X
authors.lastname: Huang
authors.forename: K
authors.initials: K
authors.lastname: Lu