Evolution of microstructure, mechanical and corrosion properties of Fe–13Cr–4Al-1.5Nb alloy aged at 450 °C

In the present work, the microstructure evolution, mechanical and corrosion properties of Fe–13Cr–4Al-1.5Nb alloys were systematically studied after the long-term thermal aging treatment. After aging, the Fe–13Cr–4Al-1.5Nb alloys are still mainly composed of α-Fe phase and a small amount of Fe2Nb-type laves phase, but the preferred orientation almost disappeared. With the increase of aging time, the average grain size of Fe–13Cr–4Al-1.5Nb alloy increased obviously and the amount of Fe2Nb-type laves phase also increased significantly. After aging at 450 °C for 2000 h, some coarse grains were observed in the Fe–13Cr–4Al-1.5Nb alloy and it exhibited much coarser grains with an average grain size of 19.7 μm than unaged Fe–13Cr–4Al-1.5Nb alloy due to the incomplete recrystallization. With the increase of aging time, the tensile strength was almost unchanged while the ductility decreased significantly. Due to the incomplete recrystallization, the Fe–13Cr–4Al-1.5Nb alloy exhibited the highest tensile strength of 670.5 MPa but the worst elongation of 3.9% after aging at 450 °C for 2000 h. In addition, the electrochemical corrosion test results showed that the unaged Fe–13Cr–4Al-1.5Nb alloy has better comprehensive corrosion resistance than the aged Fe–13Cr–4Al-1.5Nb alloy in 3.5wt.%NaCl solution.