Fatigue behavior of an Fe48Cr15Mo14 Er2C15B6 amorphous steel

Four-point-bend fatigue experiments were conducted on the Fe48Cr15Mo14Er2 C15B6 bulk metallic glass (BMG), amorphous steel, under load control, employing an electrohydraulic machine, at a frequency of 10 Hz (using a sinusoidal waveform) with an R ratio of 0.1, where R = σmin./σmax.(σ min. and σmax. are the applied minimum and maximum stresses, respectively). The test environment was laboratory air. Fe48Cr15Mo14Er2 C15B6 exhibited a high fatigue-endurance limit (682 MPa), which is found to be greater than those of the Zr-based BMG, Al-alloy, and high-nitrogen steel. However, the stress versus number of fatigue cycles curve of Fe48Cr15Mo14 Er2C15B6 revealed that the lifetime decreased abruptly with increasing the applied stress. The fatigue-fracture morphology indicated that Fe48 Cr15Mo14Er2C15 B6 has a significantly brittle fracture mode. Some fatigue cracks initiated from the inclusions or porosities, and the fatigue-crack propagation region was large. However, other cracks initiated from the outer tensile surface of the specimen, and the fatigue-crack propagation region was very small. The mechanisms of fatigue-crack initiation are suggested. © 2007 Materials Research Society.