Structural-phase characteristics and mechanical properties of TWIP steel Fe-24Mn-11Al-1,4C

Abstract

TWIP steels belong to a number of modern innovative structural materials that combine a high level of mechanical characteristics and low density, which brings their specific strength closer to the level of titanium alloys. Such steels usually do not contain deficient components and they are suitable for wide commercial industrial production. The most high-strength alloys include around 20-30 % Mn (wt.), around 10 % (wt.) Al and 1% (wt.) C. Such chemical composition brings them closer to the three-phase region, in which austenite, ferrite and k-carbides can simultaneously exist. According to this, it is possible to change mechanical characteristics of such alloys in a wide range only by heat treatment. Although in practice the best results are shown by a combination of deformation and heat treatment. The Manuscript presents a study of changes in the structural and phase characteristics and mechanical properties of the Fe-24Mn-11Al-1,4C alloy, prepared by electroslag melting, in its initial state, after deformation and annealing, and after deformation with subsequent hardening and aging. A fractographic analysis of the studied samples destruction places was also carried out. It is shown that the original sample obtained by electroslag remelting has the highest plasticity and the lowest strength, which is explained by combination of largest alloying of austenite and as-cast microstructure. The deformed and annealed sample is characterized by a pronounced fine-grained structure in which carbides are separated along the grain boundaries. Such a sample exhibits a strength greater than 1.1 GPa and the lowest ductility of 4.26 %. The deformed sample after quenching and aging has a similar structure, but the carbide inclusions are much finer, and the alloying rate of austenite is higher than the previous one. Such a sample shows the highest strength of more than 1.2 GPa and plasticity of 8.6 %. Keywords: TWIP-steels, casting, deformation and heat treatment, structural and phase characteristics, fractography, mechanical properties.