Effects of dynamic strain aging on mechanical properties of SA508 class 3 reactor pressure vessel steel

Abstract

An as-received reactor pressure vessel (RPV) steel SA508 class 3 (SA508 Cl.3) has been subjected to uniaxial tension tests in the strain-rate range of 6.67 × 10⁻⁵ s⁻¹ to 1.2 × 10⁻² s⁻¹ and the temperature range of 298 K to 673 K to investigate the effects of temperature and strain rate on its mechanical properties. It was found that the region of dynamic strain aging (DSA) was in the temperature range of 523–623 K at a strain rate of 1.2 × 10⁻³ s⁻¹, 473–573 K at 1.2 × 10⁻⁴ s⁻¹, and 473–573 K at 6.67 × 10⁻⁵ s⁻¹, respectively. Serrated stress–strain behaviors, predominately consisting of type A, B, and C, have been observed in these temperatures and strain-rate ranges. The solutes responsible for DSA have been identified to be carbon and nitrogen, and nitrogen atoms play a more important role. The relative DSA mechanisms for this RPV steel are discussed.