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

Abstract Selective dissolution of Ni(γ) in a binary Ni(γ)/Ni 3 Al(γ′) two-phase alloy was performed in an aqueous electrolyte including 1 wt.% (NH 4 ) 2 SO 4 and 1 wt.% citric acid to obtain a rough, γ′-terminated surface. The electrochemical potential for the selective dissolution was determined from the polarization curves of the γ and γ′ single-phase alloys. The selective dissolution tests proved that γ was precisely removed above 1.7 V SCE , resulting in the formation of a rough, γ′-terminated surface. Surface analyses revealed that a passive AlO x , which retarded the dissolution, was preferentially formed on γ′, resulting in a successful selective dissolution.