Creep of aluminium–magnesium open cell foam

Aluminium–5 wt.% magnesium open cell foam produced by replication and tested in tension at 300, 350 or 450 °C creeps at rates between 10−3 and 10−8 s−1. The behaviour of the foam matches that of the alloy from which it is made: three-power law creep with the same activation energy as for Al–Mg alloy creeping by viscous dislocation glide in the high stress regime and five-power law creep in the low stress regime. The model of Mueller et al. [Mueller R, Soubielle S, Goodall R, Diologent F, Mortensen A. Scripta Mater 2007;57:33], itself a simplified adaptation of previous variational estimates, predicts well the measured foam creep rates, in terms of both absolute value and dependence on temperature and applied stress. Agreement with the model of Andrews et al. [Andrews EW, Gibson LJ, Ashby MF. Acta Mater 1999;47:2853] is somewhat inferior, but nonetheless satisfactory. A strong dependence of creep rate on relative density is found; this feature is also captured by the variational estimate.