Light non-magnetic steels based on Fe – 25 Mn – 5 Ni – Al – C system

Abstract

1.7 %) contents on phase transformations, structure formation processes and mechanical properties of Fe – 25Mn – 5Ni – Al – C steels was studied theoretically and experimentally. The authors have estimated intervals of optimal crystallization regimes and subsequent deformation-thermal effects for obtaining austenitic steels with high specific strength. Measurements of hardness on the section of samples and mechanical tests in a wide interval of temperatures of cold, warm and hot deformation were performed as well as the assessment of phase structure of steels (alloys) on the basis of Fe – 25Mn – 5Ni– – Al – C. In a cast state alloy with 5 % of Al was non-magnetic, i.e. it had austenitic structure; alloys with 10 – 15 % of Al were magnetic with two-phase structure (γ + α). Aluminum considerably increases deformation resistance. At the same time values σ1 and σmax grow, i.e. also deformation hardening grows and softening processes are slowed down. With growth of deformation rate, influence of Al becomes stronger. Austenitic high-manganese alloys with 5 % of Al both with low and with high content of carbon have rather high plasticity and durability, and differ in high stability of austenite. Alloying with nickel increases plasticity. Alloys with Al less than 10 % are rather plastic also in a cast state. High-manganese (from 25 % of Mn) alloys with Al content to 5 – 7 % can be considered as high-strength cold-resistant and heat-resistant with thermally and mechanically stable austenite up to carbon content ~1.5 %.