Light Non-Magnetic Steels Based on the Fe–25 Mn–5 Ni–Al–C System

The influence of aluminum (5–10%) and carbon (0.04–1.7%) contents on phase transformations, structure formation processes and mechanical properties of Fe–25 Mn–5 Ni–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. Hardness measurements on the sample section and mechanical tests in a wide interval of temperatures of cold, warm and hot deformation were performed, as well as the phase structure assessment of steels (alloys) on the basis of Fe–25 Mn–5 Ni–Al–C. In a cast state, an 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 σ_max grow, i.e., also deformation hardening grows and softening processes are slowed down. With deformation rate growth, the Al influence becomes stronger. Austenitic high-manganese alloys with 5% of Al, both with low and high carbon content, have rather high plasticity and durability, and differ in high austenite stability. 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%.