Effect of Low Temperature Aging on Hall-Petch Coefficient in Ferritic Steels Containing a Small Amount of Carbon and Nitrogen

• Published in: ISIJ International Vol. 58; no. 10; pp. 1920 - 1926
• Main Authors: Araki, Satoshi, Fujii, Kohei, Akama, Daichi, Tsuchiyama, Toshihiro, Takaki, Setsuo, Ohmura, Takahito, Takahashi, Jun
• Format: Journal Article
• Language: English
• Published: The Iron and Steel Institute of Japan 15.10.2018
• Subjects: age hardening; ferritic steel; grain boundary segregation; grain refinement strengthening; Hall–Petch relationship
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.ISIJINT-2018-130

In this study, the effect of aging treatment at 373 K on Hall–Petch coefficient (ky) was investigated by considering the change in friction stress associated with carbide/nitride precipitation in ferritic steels containing 60 mass ppm carbon or nitrogen (C60 and N60). Tensile tests revealed that the ky monotonously increased with increasing aging time in both steels. Additionally, C60 exhibited a ky value exceeding that of N60 with respect to the same aging time. The results of the 3DAP analysis and theoretical calculation for the grain boundary segregation of carbon and nitrogen indicated that the ky corresponded to the amount of carbon and nitrogen existing at the grain boundary. No difference in the effect on increments in ky between the two elements was observed. The increase in ky in C60 under the same aging condition was due to the higher amount of segregated carbon when compared with that of nitrogen.