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

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. Herein, hot deformation behavior of 12Cr‐F/M steel in a wide temperature range is investigated to imitate industrial processes. Two Arrhenius‐type constitutive equations are established with considering austenite–ferrite transformation. The microstructure evolution at different temperature and strain rate is discussed, confirming the special characteristic of two kinds of flow curves.