Effect of grain size dispersion on the strength and plasticity of nanocrystalline metals

The effect of the dispersion of the grain size distribution on the yield stress, ultimate stress, and uniform strain of nanocrystalline metals is analyzed theoretically. It is shown that, as the grain size dispersion increases, the degree of grain boundary hardening (Hall-Petch effect) of nanocrystalline materials decreases, the onset of the grain boundary softening (inverse Hall-Petch effect) shifts to smaller nanograin sizes, and the uniform strain at which necking occurs increases.