The grain boundary defect structure can be changed to advantage by appropriate mechanical and thermal treatments. Researchers continue to show interest in understanding the effects of boundary defect structure on the mechanical properties of polycrystalline metals and alloys. Grain boundary structural features such as boundary ledges have been considered as a means of strengthening in metals and alloys. Considering the various models of Hall-Petch analyses, the grain boundary strength, σg can be expressed as σg = 8αGb(l-υ)m(L/ℓ); where m is the grain boundary ledge density, L is the grain size, ℓ is the distance of dislocation source in the adjacent grain matrix from the boundary, and G, b, and υ have the usual meaning. In particular, the influence of grain boundary ledge density on the strength (hardness) of grain boundaries is considered in the present paper.In the present investigation, pure (99.98%) nickel sheet mill (hot) rolled to 0.022 in. thick was used.
