Concurrent Enhancement of Strength and Corrosion Resistance in Ultrafine-Grained Al6063 Tubes

Abstract

This paper deals with the employment of the successive ECAP method on tubular Al6063 samples and its related properties. Application of the four passes process improved yield strength, ultimate tensile strength, and hardness up to 231%, 54%, and 92% so that the increasing rate was high at the initial passes. As compared to the as-received sample, hardness distribution uniformity which was considerably reduced at the first pass was enhanced to some extent in further passes. Microstructural analyses showed the transformation of coarse-grained structure into the elongated ultrafine-grained counterpart by successive new dislocations formation, accumulations, and their final arrangements. The corrosion performance was enhanced by the addition of pass numbers through the reduction of the depth and size of pits so that the four passes sample had a denser and more stable passive layer which in turn decreased the corrosion rate and corrosion current density.