Effects of alloying elements and heat treatments on mechanical properties of Korean reduced-activation ferritic–martensitic steel

• Published in: Journal of nuclear materials Vol. 455; no. 1-3; pp. 212 - 216
• Main Authors: Chun, Y B, Kang, S H, Noh, S, Kim, T K, Lee, D W, Cho, S, Jeong, Y H
• Format: Journal Article
• Language: English
• Published: 01.12.2014
• Subjects: Alloy development; Alloy steels; Alloying additive; Alloying effects; Alloying elements; Creep (materials); Impact resistance; Zirconium
• ISSN: 0022-3115
• DOI: 10.1016/j.jnucmat.2014.05.063

As part of an alloy development program for Korean reduced-activation ferritic-martensitic (RAFM) steel, a total of 37 program alloys were designed and their mechanical properties were evaluated with special attention being paid to the effects of alloying elements and heat treatments. A reduction of the normalizing temperature from 1050 [degrees]C to 980 [degrees]C was found to have a positive effect on the impact resistance, resulting in a decrease in ductile-brittle transition-temperature (DBTT) of the program alloys by an average of 30 [degrees]C. The yield strength and creep rupture time are affected strongly by the tempering time at 760 [degrees]C but at the expense of ductility. Regarding the effects of the alloying elements, the addition of trace amounts of Zr enhances both the creep and impact resistance: the lowest DBTT was observed for the alloys containing 0.005 wt.% Zr, whereas the addition of 0.01 wt.% Zr extends the creep rupture-time under an accelerated condition. The enhanced impact resistance owing to the normalizing at lower temperature is attributed to a more refined grain structure, which provides more barriers to the propagation of cleavage cracks. Solution softening by Zr addition is suggested as a possible mechanism for enhanced resistance to both impact and creep of the program alloys.