1988 年 37 巻 413 号 p. 166-170
The precracked specimens of mild steel (JIS: SS41) were tensile tested in liquid zinc kept at various temperatures, T, and the crack propagation behavior and crack propagation mechanism were discussed.
The crack propagation velocity da/dt increased with increasing J-integral at every T. Under the same J-integral, da/dt increased with increasing T until T=803K, but da/dt decreased with increasing T beyond T=803K. The crack propagation velocity da/dt was large when the length of intergranular diffusion region was large. The crack propagation mechanism of the steel seemed to be that the zinc vapor, which adsorbed on the crack tip, diffused along the grain boundary to weaken the crack tip area. The J-integral and temperature dependency of da/dt were able to be explained to some degree by a unidimensional intergranular diffusion model.