Effect of quenching temperature on the mechanical properties of Fe-25Cr-5Al-Ti-RE ferritic stainless steel

In this study, in order to solve the brittle fracture dilemma that occurs during the production and application of Fe-25Cr-5Al-Ti-RE ferritic stainless steel, the mechanical properties of materials under different quenching temperatures and rolling states were analyzed. After being subjected to quenching heat treatments at temperatures of 600°C, 700°C, 800°C, 900°C, and 1000°C, the Fe-25Cr-5Al-Ti-RE alloy showed minimal differences in tensile strength among the treatments at 600°C, 700°C, 800°C, and 900°C. The values were around 580 MPa, which was slightly higher than the tensile strength of 541 MPa in the rolled state. However, at 1000°C, the tensile strength significantly decreased to 510 MPa, representing a reduction of 12.62 % compared to the treatment at 900°C. Regarding elongation, it increased with rising temperature and reached its peak at 800°C. Beyond this temperature, it decreased as the temperature continued to rise. The elongation at 800°C was 27.5 %, which was a 245 % increase compared to that in the rolled state, where it was 7.96 %. The effect of precipitation on the relative elongation was relatively minor. In contrast, the grain size and orientation had the most significant impact on the mechanical properties. At 600 °C and 700 °C, the grains exhibited a relatively small size, and their orientation was markedly dispersed. When the temperature reached 800 °C, large grains were generated, accompanied by a highly consistent grain orientation. At 900 °C and 1000 °C, large grains were formed, and a certain degree of deviation in grain orientation became apparent. For the Fe-25Cr-5Al-Ti-RE ferritic stainless-steel composition in this study, the equilibrium quenching temperature was approximately 800°C.