Constitutive Equation for the Hot Deformation and Microstructure Evolution of 12Cr‐F/M Steel

Abstract

Ferrite/martensite steel is an important material candidate for nuclear reactor claddings owing to its excellent mechanical properties and radiation resistance. In particular, the hot deformation behavior of 12Cr‐ferritic/martensitic (12Cr‐F/M) steel is crucial for the fabrication of cladding tubes, and experiments performed in a wide temperature range could reveal the possible thermal deformation behavior of 12Cr‐F/M steel during tube fabrication. Herein, hot compression experiments of 12Cr‐F/M steel are conducted with strain rates and deformation temperatures ranging from 0.005 to 5 s−1 and 750 to 1200 °C, respectively. According to the thermal deformation flow and thermal expansion curves of the alloy, the Arrhenius‐type constitutive equations before and after the phase transformation of 12Cr‐F/M steel are established, taking 950 °C as the critical point. The results show that for a strain rate of 0.5 s−1, the cooling intensity increases gradually with the deformation temperature. The ferrite transforms into a mixed structure of ferrite and pearlite and finally transforms into martensite. At 950 °C, the degree of austenitization of the alloy increases with the strain rate, and the texture changes from cubic to brass.