The effect of non-equilibrium grain boundary segregation on the tensile properties and the electrochemical behaviour of nickel

• Published in: Journal of materials science letters Vol. 16; no. 14; pp. 1227 - 1230
• Main Authors: LOUAHDI, R, OUAKDI, E. H, SAINDRENAN, G, LEGALL, R, BOUCENNA, A
• Format: Journal Article
• Language: English
• Published: Dordrecht Kluwer Academic Publishers 15-07-1997
• Subjects: Applied sciences; Exact sciences and technology; Fractures; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Annealing; Electrochemical corrosion; Segregation; Mechanical properties; Nickel; Tensile property; Hardness; Current density; Grain boundary; Sulfuric acid
• ISSN: 0261-8028; 1573-4811
• DOI: 10.1007/bf02765418

The material studied in the present work is nickel 270 (Wiggin alloys) made by powder metallurgy techniques from an ex-carbonyl derivative. All the results presented point to the following: an intergranular corrosion and an embrittlment of the material occurs as a result of the deformation and annealing treatment. Any appreciable reduction in strength and ductility was not noticeable before 50 min at the same temperature. This is consistent with the free energy change accompanying sulfur surface segregation in Ni being more important than that accompanying grain boundary segregation ( Delta G sub s =-140 kJ mol exp -1 , Delta G sub gb =-98 kJ mol exp -1 [22]), and therefore, depsite the fact that grain boundaries constitute a path taken by sulfur to segregate to the surface, grain boundaries become saturated only after the surface is saturated. The phenomenon is, therefore, not due to the recrystallization process itself but to the segregation of impurities (most likely sulfur, as confirmed by other studies to grain boundaries occurring during the recrystallization treatment.