Segregation and solution of iron is followed up on a commercial WFe dilute alloy by measuring electrical resistivity, thermopower and — on the fracture surface — AES. The thermopower measures practically only the solute iron concentration in this alloy. At the same time the excess electrical resistivity is sensitive mostly to the concentration of grain boundaries and the AES measures the iron accumulated on the surface of the grain boundaries. According to these measurements grain boundary segregation occurs at temperatures where the bulk diffusion is negligible yet. So this segregation can be explained only by moving grain boundaries, which “sweep over” the crystallites, accumulating the iron atoms. It turned out that only a part of the iron segregated onto the grain boundaries, the larger part segregated onto the second phases, although their total surface is about ten times less. Supposing a state close to the equilibrium, the heats of segregation is estimated to be 50 and 100 to 120 kJ/mol for segregation to grain boundaries and to second phases, respectively.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics