Ductile-Brittle Transition Temperature Measuring and Deformation Characteristics of Pure Tungsten Based on Small Punch Testing

Small punch testing was conducted on pure tungsten at different temperatures (25, 200, 300, 400, 500 ℃). The relationship between fracture energy and temperature was obtained, and then the ductile-brittle transition temperature of pure tungsten was fitted. The fracture morphology of pure tungsten after small punch testing at different temperatures was observed, and the deformation characteristics of pure tungsten during small punch testing were investigated. The results show that pure tungsten was in a completely brittle state at 25, 200 ℃, and was in a semi-brittle state at 300 ℃. When the temperature reached 400 ℃, pure tungsten showed good plasticity. The fracture energy of pure tungsten increased sharply in the range of 250–400 ℃, and the ductile-brittle transition temperature by fitting was (342±8) ℃. When the temperature was lower than the ductile-brittle transition temperature, the pure tungsten fracture had long straight cracks along the rolling direction, and the fracture characteristics changed from intergranular fracture to transgranular fracture with temperature. When the temperature was higher than the ductile-brittle transition temperature, cap extrusion morphology, annular cracks and shortmouth cracks appeared on fracture. There were a lot of dimple in the annular cracks, and the fracture characteristics were ductile fracture. A tungsten stratification phenomenon occurred in the shortmouth cracks.