KINETIC-STUDY OF SUPERFICIAL SEGREGATION OF SULFUR IN QUENCHED NICKEL

In a paper published in 1968, K. T. Aust et al. attributed local variations of microhardness in the vicinity of grain boundaries of some quenched alloys to solute segregation induced by a coupled flux of vacancies and solute atoms. According to the authors, the extent of this segregation ranged between tens and hundreds of micrometers and they concluded that intergranular segregation, as defined by McLean, must exist, even if there was no evidence of it, because of the technique used. Later, evidence of interfacial segregation induced by oversaturate vacancies has been confirmed by different authors. Such a phenomenon has also been confirmed in the case of nickel, for which the very strong segregation of sulfur is enhanced by a crystal defect excess. In this article, we show that in addition to the superficial segregation of sulfur associated with the elimination of vacancies in quenched nickel, a non-equilibrium sulfur segregation is still observed at temperature greater than those for which the electrical resistivity recovery appears.