Commercial purity Al has been processed by hot isostatic pressing consolidation of nanopowders. The resulting bulk material contained a small fraction of microcrystalline grains (>300 nm) embedded in a matrix of ultrafine grains (150 nm). The mechanical properties under compressive tests at various temperatures and at a strain rate of 2×10－4 s－1 have been investigated. At room temperature a brief hardening was observed followed by a stagnation of the flow stress up to failure. From 150 to 200℃ softening occurred after a short hardening stage. A change in the behavior showed up at 300℃: a quasi perfect plasticity was observed subsequently to a yield point. The major deformation mechanisms include dynamic recovery, grain fragmentation and sliding. Besides, when tested up to rupture at elevated temperature filament formation where observed at the fracture surface. The formation mechanism of the filaments is possibly linked to the presence of a viscous-like phase at grain boundaries.
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