MORPHOLOGIES OF THE TENSILE AND BEND FATIGUE FRACTURE SURFACE OF FE-CR-SI-B METALLIC-GLASS WIRE

The fracture surfaces of Fe-Cr-Si-B metallic glass wire samples that f ailed in either pure tension or through bending fatigue were examined by scanning electron microscopy. A classical vein pattern, previously observed for metallic glass ribbon samples that had failed at high str ess concentrations, was found on the samples fractured in tension. The fatigue fracture surface morphologies were, however, similar to those observed in ceramics and silicate glasses fractured in bending or in tension. The morphologies for the latter can be ascribed to the changi ng stress intensity during the progression of the fatigue crack. The s tress intensity at the crack branching is found to be of the same orde r of magnitude as the fracture toughness of typical ferrous metallic g lass alloy measured in tension.