The control of oxidation-induced intergranular embrittlement by grain boundary engineering in rapidly solidified Ni-Fe alloy ribbons

The relation between grain boundary microstructure and oxidation-induced intergranular embrittlement has been investigated in rapidly solidified and subsequently annealed Ni-39 mass%Fe thin ribbons with different grain boundary microstructures. These thin ribbons were heated in air under different tensile stresses to enhance intergranular oxidation. Oxidation-induced embrittlement was then evaluated by three-point bending tests. It was found that the brittleness of oxidized ribbons varied according to the grain boundary microstructure. Fine-grained microstructure was found to be superior to coarse-grained one by suppressing oxidation-induced embrittlement when the type and the frequency of grain boundaries (that is called the Grain Boundary Character Distribution, GBCD) were properly controlled. Moreover, for a given grain size, grain boundary microstructure containing higher frequencies of special boundaries was shown to be advantageous in the control of oxidation-induced intergranular embrittlement. On the basis of these findings, the importance and usefulness of grain boundary engineering for the control of oxidation-induced intergranular embrittlement are discussed.