E. Combaz

Uniaxial deformation of microcellular metals: model systems and simplified analysis

Microcellular aluminium can be produced by a process known as replication; this involves the infiltration of a packed bed of NaCl particles which are subsequently leached after metal solidification. The resulting material features a uniform distribution of equisized pores, the shape and volume fraction of which can be tailored, as can the composition and microstructure of the metal making the resulting metal “sponges”. These display a regular uniaxial stress-strain behaviour, at both room and elevated temperature, which is interpreted using standard composite models for Young’s modulus coupled with variational predictions for non-linear deformation of two-phase composites by Ponte-Castaneda and Suquet, adapted and simplified for the specific case at hand.

Deformation of Open‐Cell Microcellular Pure Aluminum Investigated by the Acoustic Emission Technique

Acoustic Emission (AE) is used to characterize the plastic deformation of open-cell pure aluminum foams produced by salt replication. Measurements were performed on samples with cells 25, 75 or 400 μm in average diameter, all with a relative density near 24%. AE signals were measured during compression tests conducted with a constant cross-head speed. Deformation is uniform along the porous metal samples. Recorded AE accompanying plastic deformation of the cellular structure exhibits intermittent behaviour, with the probabilities of AE event energies distributed according to a power-law similar to those previously found in many different materials. The present study thus confirms the universal scale-free character of global plastic deformation dynamics and extends the observation to pure aluminum.