焼もどし脆化した鋼の破面観察に関する2, 3の考察

抄録

The testing temperature dependence of the fraction of intergranular fractures was investigeted in brittled the fracture of temper embrittled low alloy steels after Charpy impact tests. Quantitative measurements of the fraction of intergranular fractures in microscopic brittle fracture, which consists of quasi-cleavage and intergranular fractures excluding ductile fracture in macroscopic brittle fracture, were made using the point count technique applied to electron microfractographs.
It was found that intergranular fracture increases with the increase of fracture temperature and transgranular (quasi-cleavage) decreases with it. Intergranular and transgranular fracture strengths were discussed following Griffith-Orowan equation for brittle fracture accompanying plastic deformation on the fracture surface, and the change in fracture modes would be attributed to the temperature dependence of the plastic energies accompanied by the formation of the fracture surface, since the plastic energies would be dominant in the effective surface energies accompanied by the brittle fracture surfaces.
The variation of the fraction of intergranular fracture as a function of phosphorus and molybdenum contents, and the intergranular fracture in temper embrittled ferritic-pearlitic steel were also investigated.