抄録
The effects of low-temperature aging of up to 313K on quenched Fe-30%Cr ferrite stainless steel alloys were investigated. Static strain-aging tests were performed on Fe-30%Cr alloy polycrystals containing 28ppm and 130ppm carbon in order to clarify the static strain-aging phenomenon at temperatures ranging between 313K and 473K. The 0.2%-proof stress decreased with increasing deformation temperature, but a hump of 0.2%-proof stress was evident from 373K to 473K. Activation energies obtained from the strain-aging tests measured about 71kJ/mol for the specimens containing 130ppm carbon and about 78kJ/mol for those containing 28ppm carbon. These values are in agreement with the activation energies for the diffusion of carbon and nitrogen in α-Fe. In our previous studies, we demonstrated that only carbon was concentrated at the front of Lüders bands after aging. Through some chemical interaction, the nitrogen may be unable to move to a dislocation due to the nitrogen having been combined with the chromium atoms. In addition, the hump of 0.2% proof stress could not be observed in specimens containing 28ppm carbon. Based on our findings, the static strain-aging phenomenon is considered to be associated with the diffusion of carbon in Fe-30%Cr. Using the activation energy, the number of jumps, dislocation density and mean dislocation distance were calculated. The calculated result for the dislocation density is in agreement with that obtained for the dislocation density at the front of Lüders band as reported in our previous paper.
