Boundary Strengthening over Five Length Scales

The strengthening effect of grain boundaries and dislocation boundaries is a traditional metallurgical theme, which at the present time is being revived. The reason is the scientific and industrial interest in strength obtained through a structural refinement. Such a refinement is found in nanocrystalline metals subdivided by grain boundaries and in heavily deformed metals subdivided by a mixture of dislocation boundaries and high angle boundaries. The structural dimension of these materials covers a scale form the nanometre range to the hundreds micrometers level i.e. five length scales. Consequently, a multiscale analysis has been applied to the relationship between strength and the boundary parameters. As an example this analysis suggests that the yield stress/grain size relationship follows the Hall‐Petch relationship down to a grain size of about 15–20 nm showing large potential for strengthening of a metal through a structural refinement.