Modelling grain boundary strengthening in ultra-fine grained aluminum alloys

The mechanical properties of aluminum alloys with grain sizes in the range from less than a micron (ultra-fine) to hundreds of microns have been modelled within the framework of the multi-parameter microstructural work hardening model developed by Nes and co-workers [E. Nes, Prog. Mater. Sci. 41 (1998) 129–194; K. Marthinsen, E. Nes, Mater. Sci. Technol. 17 (2001) 376–388; E. Nes, K. Marthinsen, Mater. Sci. Eng. A322 (2002) 176–193; E. Nes, K. Marthinsen, B. Holmedal, Mater. Sci. Technol. B 20 (2004) 1377–1382]. The effect of grain size on the flow stress and work hardening, including a deviation from the Hall–Petch grain size dependency for ultra-fine grain sizes, is well accounted for by the model. A characteristic feature of the stress–strain behaviour of Al–Mg-alloys and ultra-fine grained variants is a sharp yield point followed by Lüders-band elongation. A mechanism for such an elastic–plastic transition is suggested.