Sammendrag
By careful annealing of heavily deformed metals ultra-fine grained materials can be obtained. This phenomenon has been known for long and utilised in the production of special aluminium sheet qualities. It has received new interest with the emergence of the equal channel angular pressing (ECAP) technique, where pioneering works have been performed by T. Langdon and co-workers. In the present work 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. The effect of grain size on the flow-stress and work hardening, including a deviation from the Hall-Petch grain size dependency for ultrafine grain sizes, is well accounted for by the model. A mechanism is suggested for the sharp yield point and associated Lüder-band elongation relevant for ultra-fine grained AlMg-alloys
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