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Why do secondary cracks preferentially form in hot-rolled ODS steels in comparison with hot-extruded ODS steels?
Das, A.ORC; Viehrig, H. W.; Altstadt, E.ORC; Bergner, F.ORC; Hoffmann, J.ORC
Secondary cracks are known to absorb energy, retard primary crack propagation and initiate at lower loads than primary cracks. They are observed more often in hot-rolled than in hot extruded ODS steels. In this work, the microstructural factors responsible for this observation are investigated. Better understanding of these factors can lead to tailoring of im-proved ODS steels. Fracture toughness testing of two batches of 13Cr ODS steel, one hot-rolled and the other hot-extruded, was carried out. The fracture behaviour of secondary cracks was investigated using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Crystallographic texture and grain morphology play a predominant role in preventing secondary cracks in hot-extruded ODS steels. At lower temperatures, secondary cracks occur predominantly via transgranular cleavage. The fracture mode changes to ductile and intergranular at higher temperatures.
Keywords: ODS steel, fracture behaviour, anisotropy, intergranular fracture, secondary cracking, delamination

Publ.-Id: 27705 - Permalink