Fatigue behaviour of Fe–Cr–Si–B metallic glass wires

Cyclic compressive/tensile bending has been carried out on Fe–Cr–Si–B metallic glass wires using a controlled strain double pulley testing machine. The fatigue performance of two series of glassy alloy wires Fe78−xCrxSi10B12 and Fe77.5−xCrxSi7.5B15 have been compared with those of HT steel wires. Because of differences in modulus, the ranking of the materials studied changes according to whether the results are reported in terms of stress or strain. In terms of stress, the HT steel wire had a superior fatigue performance to the glassy wires; however, in terms of strain, the Fe69.5Cr8Si7.5B15 glassy wire, under higher cycle conditions, had a superior fatigue performance, to HT steel wire. The fatigue performance of the glassy wires improved with the partial substitution of Fe by Cr. The short fatigue life of the glassy wires containing zero or low Cr contents in the present study was at least partly due to the necked morphology along their lengths. Fractography revealed that corrosion pits nucleated on the surface of the wires and resulted in crack initiation at these points.