Modelling grain boundary strengthening in aluminium alloys

ABSTRACT The mechanical properties of aluminium 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 (Nes 1998; Marthinsen and Nes 2001; Nes and Marthinsen 2002; Nes, Marthinsen and Holmedal 2004). 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 AlMg-alloys and ultra-fine grained variants is a sharp yield point followed by Lüder-band elongation. A mechanism for such an elastic-plastic transition is suggested.