DBPapers
DOI: 10.5593/SGEM2014/B61/S24.024

THE LONG TERM CORROSION BEHAVIOR OF A SHAPE MEMORY ALLOY IN SEAWATER SUBJECTED TO VARIOUS PLASTIC DEFORMATION PROCESSES

C. Gurau, G. Gurau, F. Potecasu
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-20-9 / ISSN 1314-2704, June 19-25, 2014, Book 6, Vol. 1, 173-180 pp

ABSTRACT
The influence of the microstructure on the corrosion behavior of a CuAlNi
polycrystalline alloy has been studied. The aim of this work was to compare corrosion of shape memory bronze in cast state, after extrusion, rolling, ausforming, marforming and high speed high pressure torsion severe deformation, in Black See water throughout six years. Chloride environment can affected different the alloy, producing dealuminization attack, when lost of aluminum from alloy leave a porous residue of cooper Cu2O film. The martensitic phase suffers generalized dealuminization on the whole surface and function of the manufacturing process in specific regions appears localized corrosion. The environmental factor affects the formation of the various cooper salts, damaging the compact protective aluminum layer. The seawater provided by coast zone is polluted that leads to form sulfur compounds, hydrogen sulfide and can be contaminated with nitrogen compounds from decomposing algae and plankton. The aluminum bronze are corrosion susceptibility especially at decay of organic matter. Attention was paid to the corrosion process associated with the structural changes from dendritic microstructure to ultrafine martensitic grains. In order to enhance the surface corrosion resistance, shape memory alloy is subjected to accentuated crystalline grain refining. Optical microscopy was performed on the surface of the specimens and also in cross section at different moments during the long time exposure to sea water. The SEM observation was done on the surface of specimens. The EDX analytical examination after conditioning used for the elemental analysis showed formation of Cu and Al oxide layer in case of ausformed samples that suggest improves the corrosion stability.

Keywords: CuAlNi, Shape memory alloy, Corrosion behavior, Dealuminization
corrosion, Microstructure, EDX