Effect of Al Additions and Cooling Rate on the Microstructure and Mechanical Properties of Austenite FeMnAlC Steels

Abstract

The precipitation behavior of κ-carbide and its effects on mechanical properties in Fe-30Mn-xAl-1C (x = 7–11%) steels under water quenching and furnace cooling are studied in the present paper. TEM, XRD, EPMA were employed to characterize the microstructure, and tensile test and the Charpy impact test were used to evaluate mechanical properties. The results show that the density decreases by 0.1 g/cm3 for every 1 wt.% of Al addition. The excellent mechanical properties of tensile strength of 880 MPa and impact absorption energy of 120–220 J at −40 °C with V notch were obtained, with both solid solution and precipitation strengthening results in the yield strength increasing by about 57.5 MPa with per 1% Al addition in water-quenched samples. The increasing of yield strength of furnace-cooled samples comes from the relative strengthening of κ-carbides, and the strengthening potential reaches 107–467 MPa. The lower the cooling rate, the easier it is to promote the precipitation of κ-carbides and the formation of ferrite. The partitioning of C, Mn, Al determines the formation of κ-carbides at a given Al addition, and element partition makes the κ-carbides sufficiently easy to precipitate at a low cooling rate. The precipitation of κ-carbides improves strength and does not significantly reduce the elongation, but significantly reduces the impact absorption energy when Al addition ≥ 8%.

Features and Restrictions of Electroslag Remelting with Silica‐Bearing Slags for Lightweight High Manganese Steel

“…Performed calculations of the phase composition in the system Fe- (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)Mn-(10-12.0)Al-1-2 C (wt%) indicate that in the considered range of concentrations, the appearance of undesirable phases during hardening is possible. Therefore, for such steels, it is crucial to ensure a stable composition and favorable solidification conditions to obtain a uniform structure: the cooling rate should be high but not cause cracks in the surface area.…”

“…Such lightweight steels have up to a 17% less specific density and belong to the system Fe–Mn–Al (and/or Si)–C with high content of manganese (18–30 wt%), carbon (0.6–1.8 wt%), aluminum (up to 12 wt%), and/or silicon (up to 3 wt%). [ 28–30 ]…”

“…For example, each 1 wt% of aluminum reduces it to 1.5%. [ 4,31,32 ] Previous studies [ 28,29 ] have proved 0.1 g cm −3 of density reducing for every 1 wt% of Al addition. The idea of significant additions of aluminum to sheet steels was not brand‐new: early grades for cryogenic applications consist of 3%–5% of aluminum.…”

“…[27] Such lightweight steels have up to a 17% less specific density and belong to the system Fe-Mn-Al (and/or Si)-C with high content of manganese (18-30 wt%), carbon (0.6-1.8 wt%), aluminum (up to 12 wt%), and/or silicon (up to 3 wt%). [28][29][30] The manganese austenite as the matrix and light elements additions provide steels with low specific density. For example, each 1 wt% of aluminum reduces it to 1.5%.…”