Segregation phenomena in molybdenum containing voids

The stage of void formation and the depth of impurity position near the void surface in the unalloyed commercial molybdenum and in the molybdenum alloy is firstly studied. Sudden segregation of impurity and alloying elements considerably exceeding segregation on grain boundaries is shown to be observed in the near-the-surface layer of voids of the Mo welded joint. The width of the segregation zone of different elements decreases in the C, O, Y, N, B, K, S series. As on the very surface voids segregate most of all S, K, O, N, which are dongerous impurities with low surface energy, than one may state that segregation effects lead to sharp decrease of surface energy in the void. Due to this fact segregation phenomena promote brittle