The Novel Combination of Strength and Ductility in 0.4C‐7Mn‐3.2Al Medium Manganese Steel by Intercritical Annealing

Abstract

By altering the temperature and duration of intercritical annealing (IA), the mechanical stability of retained austenites (RAs) is intentionally regulated in newly designed cold-rolled medium manganese steel of Fe-0.4C-7Mn-3.2Al (in wt%). Consequently, a novel combination of ultimate tensile strength (UTS) and total elongation (TE) (e.g., 1118 MPa and 67%) is obtained in duplex steel, and the corresponding product of UTS and TE can reach 75 GPa%. Both twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) take effect step by step during deformation and are conducive to the outstanding properties.

Modulating Mechanical Properties of Fe–0.35C–3.2Al–5Mn Hot‐Rolled Steel by Combining Twinning‐Induced Plasticity plus Transformation‐Induced Plasticity Effect

“…Figure S4, Supporting Information, shows the true stress–strain and true strain–work hardening rate (WHR) curves which are divided into different stages of the investigated steels’ intercritical annealing at different temperatures. The WHR in S I is characterized by the dramatic decrease which is attributed to the elastic deformation and softening of the matrix phase, [ 9,25 ] whereas S II and S III with a relatively lower WHR at 650 and 700 °C are attributed to the competition of lattice distortion due to dislocation slip with softening of the matrix phase. The WHR curve at 750 °C is divided into four stages, S I , S II , and S III are discussed above and S IV will be discussed later, combined with TEM micrographs and V RA at various true strains.…”

“…Thus, the severe fluctuation of WHR in S IV is due to the competition of the obvious TRIP effect and apparent TWIP effect, as we reported previously. [ 9 ]…”

“…The research of strengthening mechanism and deformation behavior in intercritical annealed Fe–0.4C–3.2Al–7Mn cold‐rolled medium‐manganese steel was taken from our previous work. [ 9 ]…”

Volatilization Behavior of Manganese from Molten Steel with Different Alloying Methods in Vacuum

“…where is the molar fraction of manganese in the molten steel; is the Raoultian activity coefficient of Mn; and and are the activity coefficient and mass percentage based on 1% concentration in Henry's Law. According to Wagner's model [19], the interaction coefficients (Table 4) at the same temperature (1873 K) are used to calculate the activity coefficients in Equation (3).…”

“…Manganese is an indispensable alloying element in steel, owing to its ability to significantly improve the strength and toughness of steel through solid solution strengthening and dispersion strengthening mechanisms [1,2]. In particular, medium manganese steels (5-12 wt% Mn) as the third-generation advanced high-strength steels (AHSS) are in the limelight, and this is attributed to their exhibiting extraordinary combination of ultra-high strength, excellent plasticity, and low production costs, leading to great applications in automotive, construction, and high-speed trains industries [3][4][5][6]. In recent years, the microstructure and mechanical properties of medium manganese steels have been extensively studied [7,8].…”