Abstract
The creep behaviour of pure polycrystalline aluminium and single crystals processed by equal-channel angular pressing (ECAP) was investigated in order to understand the relationships between heterogeneity of microstructure and creep behaviour. Tensile creep tests were performed at 373 K on specimens processed by 1 and 4 ECAP passes. For comparison purposes, the creep tests were also carried out on coarse-grained specimens. Microstructure analyses showed that application of ECAP technique on polycrystalline aluminium and single crystals led to the formation of significantly different microstructures even after a relatively high number of ECAP passes. The different creep behaviour of ECAP-processed single crystals and polycrystalline aluminium is influenced by inhomogeneity of microstructure. Further, the creep behaviour of specimens processed by 4 ECAP passes is affected by grain-boundary mediated processes like enhanced recovery of dislocations at high-angle grain boundaries in grains finer than quasi-stationary subgrain size and grain boundary sliding.

Key words
equal channel angular pressing (ECAP), aluminium, ultrafine-grained microstructure, creep

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