Notch sensitivity of two materials including TiAl alloys and K418 alloys

摘要

The tensile sensitivity of notch specimens has been investigated for TiAl alloys and K418 alloys. The notch strength has been quantitatively analyzed. Fracture surfaces of series specimens are also observed and analyzed by scanning electron microscopy (JEOL-6700F). By comparison with series results of notch rod tensile specimens and the special notch rod tensile specimens, it can be found that: Ductile fracture (tear ridge) and dendriage fracture dominate fracture surface of K418 alloys, however, quasi-cleavage fracture including interlamellar fracture and translamellar fracture dominate fracture surface of TiAl alloys. The basic nature of two materials are different, and the driving force of fracture and fracture criteria are also different for brittle TiAl alloys and ductile K418 alloys. For K418 alloys, the final fracture of specimens is controlled by strain not by stress, no notch sensitivity is existed in K418 alloys. However, for TiAl alloys, the final fracture of specimens is controlled by stress, smaller notch sensitivity is existed in TiAl alloys. For special notch rod tensile specimens, no notch sensitivity still appear for K418 alloys. However, for TiAl alloys, when notch depth reaches 10% of specimen diameters, tensile strength decrease. When notch depth reaches 20% of specimen diameters, tensile strength sharply decrease, these parameters are regarded as a important parameter estimating notch depth or depth of casting defect.