Effect of Manganese, Carbon and Nitrogen on High-Temperature Strength of Fe-Cr-Mn Alloys

Tensile properties of Fe-12%Cr-Mn(mass%) alloys have been studied in the temperature range between room-temperature and 1073 K. Mn contents of the alloys are ranged from 5 to 30%. The tensile properties of Fe-12%Cr-Mn alloy is markedly affected by Mn content. Relatively high strength and low ductility are obtained in 5 and 10%Mn alloys which consist of mainly α′-martensite structure at temperatures below 673 K. The transformation from α′-martensite to austenite results in a large drop of tensile strength and an increase of ductility. The tensile strength of the 15%Mn alloy decreases linearly with increasing test temperature. In the case of the 20%Mn alloy. The tensile strength decreases rapidly at temperatures up to 473 K where ε-martensite transforms to austenite, and it decreases gradually with increasing temperature. In the austenite range, the tensile properties scarcely depend on Mn content.C and N additions improve the tensile properties of the Fe-12%Cr-15%Mn alloy markedly. Combined alloying of 0.2%C and 0.2%N with the alloy makes the strength as high as that of JPCA (0.05%C-15%Cr-16%Ni-2.5%Mo-0.2%Ti steel), increases the creep strength pronouncedly and decrease the steady state creep rate.