Effects of grain size from millimeters to nanometers on the flow stress of metals and compounds

Abstract

The effect of grain size d from millimeters to nanometers on the flow stress σ of metals and compounds is considered. The data for metals indicate three grain regimes: I (d≥1 µm), II (d ≠ 10–1,000 nm), and III (d<∼10 nm). Grain size hardening occurs in I and II and grain size softening occurs in III. The data for compounds suggest similar regimes, but are too limited for positive identification. The physical mechanisms governing each regime are discussed. The data for regime III are in reasonable accord with the mechanism of grain boundary shear proposed by Conrad and Narayan.