Selective dissolution of the gamma phase in a binary Ni(gamma)/Ni3Al(gamma ') two-phase alloy

Abstract

Selective dissolution of Ni(gamma) in a binary Ni(gamma)/Ni3Al(gamma') two-phase alloy was performed in an aqueous electrolyte including 1 wt.% (NH4)(2)SO4 and 1 wt.% citric acid to obtain a rough, gamma'-terminated surface. The electrochemical potential for the selective dissolution was determined from the polarization curves of the gamma and gamma' single-phase alloys. The selective dissolution tests proved that gamma was precisely removed above 1.7 V-SCE, resulting in the formation of a rough, gamma'-terminated surface. Surface analyses revealed that a passive AlOx, which retarded the dissolution, was preferentially formed on gamma', resulting in a successful selective dissolution. (C) 2010 Elsevier Ltd. All rights reserved.