抄録
The casted AC7A in which Zn content is 4 /0wt% was used as base material. In order to discuss the effect of heat treatment on its hydrogen embrittlement characteristics, 3 types of heat treatment were conducted. None heat treated(F) material, solution treated(T4) material and both of solution and aging treated(T6) material were prepared. The heat treated material was machined to V-notched tensile specimen to evaluate the hydrogen embrittlement characteristics at corrosive environment under constant load 1wt% of NaCl solution was used as the corrosive media. Micro structure and behavior of hydrogen generation of those materials were also evaluated by the optical microscope and fixed point observation by digital camera. Test results were as follows micro structure observation suggested that the amount of inclusion was decreased when heat treatment(T4,T6) was conducted. Microscopic observation also showed that the hydrogen was generated from the boundary of inclusion. Thus, the amount of hydrogen generation of heat treated specimen was fewer than that of the none treated specimen. Test results also showed that the amount and rate of hydrogen generation was increased when the stress was applied to the specimen. The hydrogen embrittlement test showed that the time until failure was increased with decreased of applied tensile stress. The critical strength at corrosive environment was also increased when the heat treatment was conducted. Finally, this paper revealed that the ageing treatment was effective to prevent the degradation of the tensile strength under the corrosive environment.
