Materials Transactions, Vol.51 No.01 (2010) pp.8-13
© 2010 The Japan Institute of Metals

Rate Independent and Rate Dependent Structural Evolution during Severe Plastic Deformation

Andrea Bachmaier, Martin Hafok and Reinhard Pippan

High pressure torsion (HPT) deformation enables the grain refinement of bulk materials until a saturation region is reached where no further microstructural refinement can be observed. The influence of deformation temperature, alloying and strain rate on the saturation region was examined by using pure aluminum, an Al-1 mass%Mg alloy and an Al-3 mass%Mg alloy. The deformation temperature was varied between -196°C and 450°C. Both, temperature and alloying exhibit a pronounced influence on the saturation microstructure. The measurements reveal either a rate independent behavior of the structural evolution at low temperatures and a rate dependent behavior of the structural evolution at high temperatures. Two different processes are proposed to be the reason for the saturation at low and high homologous temperatures.

(Received 2009/8/17; Accepted 2009/10/2; Published 2009/12/25)

Keywords: aluminium alloy, high pressure torsion, saturation, grain boundary migration, strain rate

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