ニッケル・銅二元合金における表面偏析

概要

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A newly developed focusing-type time-of-flight atom-probe (field ion microscope) was applied for the detailed investigation of surface segregation in Ni-Cu binary alloys over the entire composition range. Strong enrichment of copper was observed in the Ni-rich alloys, in agreement with previous reports. The surface enrichment factor and heat of Cu segregation were determined experimentally and were found to agree with various theoretical results. Cu segregation was limited to the topmost surface layer in almost all of the cases. The adjacent subsurface region exihibited small oscillations in the composition. A surprising finding was that nickel segregated to the surface in the Ni solute region (less than 16 at.% Ni). The Ni segregation extended over several layers in the near-surface region, a marked difference compared to the case of the Cu segregation. At present no theory on surface segregation can explain the Ni segregation.
日本真空協会の論文