Surface oxide in replicated microcellular aluminium and its influence on the plasticity size effect

The oxide film present along the interface between metal and pores in microcellular aluminium produced by replication depends on the leaching medium that is used to dissolve the NaCl preform: leaching in water produces a thick and irregular multilayered hydroxide layer, whereas leaching in a chromate conversion solution produces a smooth layer of oxide, ≈10 nm thick. The pore-size-dependent flow stress of replicated microcellular aluminium exhibits a marked dependence on the leaching process used to produce the foam when the pore size is below roughly 100 μm. This dependence on the leaching medium is a result of the influence exerted by the outer surface oxide layer on dislocational glide in micron-sized metal struts making the foam.