Purpose: The aim of this paper is to determine the high-manganese austenite propensity to twinning induced by the cold working and its effect on structure and mechanical properties, and especially the strain energy per unit volume of new-developed high-manganese Fe-Mn-(Al, Si) investigated steels, including selected high-manganese austenitic TWIP steels containing 25-27.5% Mn, 1-4% Si, 2-3% Al, high-manganese TRIP steels containing 17-18% Mn, about 1% Si, about 3% Al and selected high-manganese TRIPLEX steels containing 24% Mn and about 11% Al and some of that steels with Nb and Ti microadditions, with various structures after their heat- and thermo-mechanical treatments. Design/methodology/approach: The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopies as well as X-ray diffractomiter. Findings: New-developed steels achieve profitable connection of mechanical properties, i.e. (ultimate tensile strength) UTS~800-1000 MPa, (yield strength) YS0.2 = 250-450 MPa, and plastic (uniform elongation) UEl = 35-90%, and moreover, particularly strong formability and strain hardening occurring during forming. The new-developed high-manganese Fe-Mn-(Al, Si) steels provide an extensive potential for automotive industries through exhibiting the twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) mechanisms. Practical implications: The obtained microstructure - hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures. Originality/value: Results obtained for new-developed high-manganese austenitic steels with the properly formed structure and properties in the heat treatment- or thermo-mechanical processes indicate the possibility and purposefulness of their employment for constructional elements of vehicles, especially of the passenger cars to take advantage of the significant growth of their strain energy per unit volume which guarantee reserve of plasticity in the zones of controlled energy absorption during possible collision resulting from activation of twinning for TWIP steels, supported with martensitic transformation for TRIP steels, induced cold working, which may result in significant growth of the passive safety of these vehicles’ passengers.
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