Twofold age-hardening mechanism of Al-added high-Cr ODS ferritic steels

作者：Kimura, Akihiko; Sang, Wei; Han, Wentuo; Yabuuchi, Kiyohiro; Xin, Zongxi; Luan, Junhua; Dou, Peng^*

来源：Journal of Nuclear Materials, 2023, 575: 154223.

DOI：10.1016/j.jnucmat.2022.154223

• Oxide dispersion strengthened (ODS)
• ferritic steel
• Age-hardening
• fi? phase
• ?-?? phase separation
• Atom probe tomography

Age-hardening of oxide dispersion strengthened (ODS) ferritic steels with various contents of Cr and Al was investigated by Vickers hardness (HV) measurement and tensile test after ageing at 475 degrees C for up to 90 0 0 h. The correlation between age-hardening and the evolution of nanometer-scale structure and chemistry studied by atom probe tomography (APT) reveals that the age-hardening could be interpreted in terms of twofold hardening mechanism involving alpha-alpha' phase separation and/or the precipitation of (Al, Ti)-enriched fi' phases. The results of APT characterization indicate that the Cr concentration and volume fraction of alpha' phase increase significantly while the chemical compositions and volume fraction of fi' phases don't changed considerably during ageing from 300 h to 90 0 0 h. At the early stage of age-ing, the age-hardening due to alpha-alpha' phase separation is very limited because of the low Cr concentration of alpha' phase, which results in very weak modulus strengthening. With the increasing of ageing time, the age-hardening is increased because of the increasing of Cr content in the alpha' phase, resulting in consider-ably enhanced modulus mismatch strengthening. However, age-hardening due to fi' phase precipitation is significant once the fi' phases are formed and, thereafter, it doesn't change apparently. The metal/oxide interfaces in ODS steels provide nucleation sites for alpha' and fi' phases. Based on the comprehensive data developed, the roles of Cr and Al in the age-hardening of ODS ferritic steels were elucidated.

• 单位
  重庆大学; 北京科技大学