Influence of microstructure on mechanical properties and corrosion behaviour in TWIP steels

This study aims to develop and characterise a low-cost Fe-14Mn-0.4 to 0.6C-3Al-4Si-0.2Ti steel for structural applications by optimising its microstructure through controlled heat treatment. The alloy was heated to 950°C and quenched in various media (brine, water, oil, air, and a furnace) to obtain varying martensite and austenite phase fractions. Microstructural evolution, mechanical properties, density, and corrosion behaviour were systematically evaluated. Among all conditions, the brine-quenched sample exhibited the highest microhardness (441 ± 4 HV) and tensile strength, (~1400 MPa) due to its increased martensite content, while maintaining a low density of 6.99 ± 0.05 g/cm³. In contrast, the air cooled sample, characterized by a predominatly austenitic microstructure with ~9% deformation twins, showed the best corrosion resistance, with corrosion rate of 0.0504 mpy and minimum weight loss of 0.002. Rapid cooling conditions, such as brine quenching (Icorr = 0.389 A/cm²), increased corrosion susceptibility because of limited formation of protective surface films. Slower cooling methods, including furnace cooling (Icorr = 0.048 A/cm²) and air cooling (Icorr = 0.051 A/cm²), enhanced corrosion resistance through the development of stable and protective oxide layers.