Fracture process in tensile testing dental Ni-base casting alloys.

Early-fracture in tensile specimens was found in Ni-base casting alloys which were obtained in conventional casting condition. In 32 Ni-23 Cu-25 Mn alloy, intercrystalline fracture occurred in both early-fractured and normal ductile specimens. On the contrary, intercrystalline and innercrystalline fracture were, respectively, found in early-fractured and normal samples. As the fracture process, voids formed by stress-concentration around A-grain and brittle fracture of soft B-grain in 32 Ni-23 Cu-25 Mn alloy, while voids occurred by stress-concentration around inclusion as chromium carbide and slip deformation on the maximum shear stress plane in 84 Ni-9 Cr alloy.