Atom probe study of the segregation behaviour of molybdenum containing alloys

Three-dimensional atom probe measurements have been carried out to study the segregation behaviour of alloys selected from the binary systems tungsten-molybdenum and platinum-molybdenum. Depth profiling analysis on in situ annealed W-Mo alloy specimens shows surface enrichment of Mo, the component with lower sublimation heat, in the first atomic layer, as predicted from theoretical model calculations. On the 95Pt5Mo alloy after annealing the changes in the local composition are not limited to the first atomic layers. The measured depth profiles indicate for the formation of an intermediate phase on the surface which can be explained on the basis of the complex phase diagram of the binary system Pt-Mo. (C) 1997 Elsevier Science Ltd.