タングステンの高温破壊じん性と破面形態

抄録

Tensile and fracture toughness tests of tungsten specimens were carried out at elevated temperatures to investigate the temperature dependences of mechanical properties and fracture toughness. Fracture surfaces were also observed in detail. Fracture toughness of tungsten was low in the temperature range lower than 1200K, at which the brittle-ductile transition was found. Fracture toughness was high in the temperature range higher than 1200K. However, the ductile-brittle transition was observed around 1500K, at which recrystallization occurred, and fracture toughness significantly decreased. On the basis of fractographic observations, quasi-cleavage fracture was dominant in the temperature range lower than the brittle-ductile transition temperature. Dimple fracture was dominant in the temperature range higher than the brittle-ductile transition temperature. However, intergranular fracture was dominant in the higher temperature range where recrystallization occurred. No significant difference in the above mentioned fracture behaviors between the recrystallized and the as-received specimens was found.