We investigated the thermodynamics and kinetics of carbide precipitation in a cold-rolled Fe-7Mn-0.1C-0.5Si medium manganese steel during low temperature tempering. The material was annealed up to 24 h at 450 C in order to follow the...
moreWe investigated the thermodynamics and kinetics of carbide precipitation in a cold-rolled Fe-7Mn-0.1C-0.5Si medium manganese steel during low temperature tempering. The material was annealed up to 24 h at 450 C in order to follow the kinetics of precipitation. Using thermodynamics and kinetics simulations , we predicted the growth of M 23 C 6 carbides according to the local-equilibrium negligible partition (LENP) mode where carbide growth is controlled by the diffusion of carbon, while maintaining local chemical equilibrium at the interface. Atom-probe tomography (APT) measurements performed on samples annealed for 1, 6 and 24 h at 450 C confirmed that LENP is indeed the mode of carbide growth and that Mn segregation is necessary for the nucleation. Additionally, we observed the heterogeneous nucleation of transition carbides with a carbon content between 6 and 8 at% at segregated dislocations and grain boundaries. We describe these carbides as a complex face-centered cubic transition carbide type (CFCC-TmC phase) obtained by the supersaturation of the FCC structure by carbon that will act as precursor to the more stable g-M 23 C 6 carbide that forms at the dislocations and grain boundaries. The results suggest that the addition of carbon does not directly favor the formation of austenite, since Mn is consumed by the formation of the carbides and the nucleation of austenite is thus retarded to later stages of tempering as every FCC nucleus in the initial stages of tempering is readily converted into a carbide nucleus. We propose the following sequence of transformation: (i) carbon and Mn co-segregation to dislocations and grain boundaries; (ii) formation of FCC transition carbides; (iii) growth controlled according to the LENP mode and (iv) austenite nucleation and growth.
Ultrafine ferrite grains in a plain C–Mn steel (0.3 mass% C) were produced by large-strain warm compression and subsequent annealing treatment in a temperature range between 773 K and 1003 K. The samples were investigated by means of...
moreUltrafine ferrite grains in a plain C–Mn steel (0.3 mass% C) were produced by large-strain warm compression and subsequent annealing treatment in a temperature range between 773 K and 1003 K. The samples were investigated by means of high-resolution electron back-scatter diffraction. The resulting microstructures showed very fine ferrite grains and homogeneously distributed cementite particles. The majority of the grain boundaries (55–70%) were classified as high-angle ones (≥ 15 misorientation). When considering only ...
Abstract We report on the microstructure, texture and deformation mechanisms of a novel ductile lean duplex stainless steel (Fe–19.9 Cr–0.42 Ni–0.16 N–4.79 Mn–0.11 C–0.46 Cu–0.35 Si, wt.%). The austenite is stabilized by Mn, C, and N...
moreAbstract We report on the microstructure, texture and deformation mechanisms of a novel ductile lean duplex stainless steel (Fe–19.9 Cr–0.42 Ni–0.16 N–4.79 Mn–0.11 C–0.46 Cu–0.35 Si, wt.%). The austenite is stabilized by Mn, C, and N (instead of Ni). The microstructure is characterized by electron channeling contrast imaging (ECCI) for dislocation mapping and electron backscattering diffraction (EBSD) for texture and phase mapping. The material has 1 GPa ultimate tensile strength and an elongation to fracture of above 60%. The ...
It is well known that during the hot rolling of Al-alloys a strong B-orientation (011)[lt]211[gt] develops at the mid layer. Furthermore, in hot rolled Al-plates a strong through thickness texture gradient arises. These effects are most...
moreIt is well known that during the hot rolling of Al-alloys a strong B-orientation (011)[lt]211[gt] develops at the mid layer. Furthermore, in hot rolled Al-plates a strong through thickness texture gradient arises. These effects are most pronounced in high strength Zr-containing Al-alloys (7XXX, 8XXX series) which do not recrystallize during hot rolling and where the strong texture causes a marked
Large strain warm deformation at different temperatures and subsequent intercritical annealing has been applied to obtain fine grained (2.4 μm) and ultrafine grained (1.2 μm) ferrite/martensite dual-phase (DP) steels. Their mechanical...
moreLarge strain warm deformation at different temperatures and subsequent intercritical annealing has been applied to obtain fine grained (2.4 μm) and ultrafine grained (1.2 μm) ferrite/martensite dual-phase (DP) steels. Their mechanical properties were tested under tensile and impact conditions and compared to a hot deformed coarse grained (12.4 μm) reference material. Both yield strength and tensile strength follow a Hall–Petch type linear relationship, whereas uniform elongation and total elongation are hardly affected by grain refinement. The initial strain hardening rate as well as the post-uniform elongation increase with decreasing grain size. Ductile fracture mechanisms are considerably promoted due to grain refinement. Grain refinement further lowers the ductile-to-brittle transition temperature and leads to higher absorbed impact energies. Besides the common correlations with the ferrite grain size, these phenomena are explained in terms of the martensite particle size, shape and distribution and the more homogeneous dislocation distribution in ultrafine ferrite grains.▶ Grain refinement leads to increase in strength, ductility is less affected. ▶ Grain refinement enhances initial strain hardening rate. ▶ Impact toughness is improved due to grain refinement. ▶ Grain refinement promotes ductile fracture mechanisms.
Résumé/Abstract The limits of strength and ductility of a medium-carbon silicon chromium spring steel are investigated for the case of conventional heat treatment including austenitization, quenching and tempering. The effect of...
moreRésumé/Abstract The limits of strength and ductility of a medium-carbon silicon chromium spring steel are investigated for the case of conventional heat treatment including austenitization, quenching and tempering. The effect of phosphorus and austenite deformation prior to quenching was studied by measuring mechanical properties after quenching and tempering and by microstructural investigation. Strong influence of phosphorus on the ductility is observed for the quenched and tempered martensite without ...
Résumé/Abstract The austenite grain coarsening behaviour in a medium carbon Si-Cr spring steel with and without vanadium was investigated by the thermal etching method. This method is efficient when the austenitization temperature is not...
moreRésumé/Abstract The austenite grain coarsening behaviour in a medium carbon Si-Cr spring steel with and without vanadium was investigated by the thermal etching method. This method is efficient when the austenitization temperature is not lower than 900 C. The average grain sizes on the surfaces of the samples determined by thermal etching vary little from those in the bulk as revealed by chemical etching. The austenite grain coarsening behaviour of the steel with vanadium can be classified in three temperature regimes. ...
Résumé/Abstract The current study on a medium-carbon steel (0.36% C) with deformation-induced spheroidized cementite produced by heavy warm deformation (HWD) was carried out in order to investigate an alternative microstructural route...
moreRésumé/Abstract The current study on a medium-carbon steel (0.36% C) with deformation-induced spheroidized cementite produced by heavy warm deformation (HWD) was carried out in order to investigate an alternative microstructural route when compared to conventional quenching and tempering (QT) or soft annealing (SA) processes. After austenite deformation, the HWD samples were cooled and heavily deformed at temperatures below the γ-α transformation followed by a simulated coiling treatment. In ...
ABSTRACT Partial reversion of interlath austenite nano-films is investigated as a potential remedy for hydrogen embrittlement susceptibility of martensitic steels. We conducted uniaxial tensile tests on hydrogen-free and pre-charged...
moreABSTRACT Partial reversion of interlath austenite nano-films is investigated as a potential remedy for hydrogen embrittlement susceptibility of martensitic steels. We conducted uniaxial tensile tests on hydrogen-free and pre-charged medium-Mn transformation-induced plasticity-maraging steels with different austenite film thicknesses. Mechanisms of crack propagation and microstructure interaction are quantitatively analyzed using electron channelling contrast imaging and electron backscatter diffraction, revealing a promising strategy to utilize austenite reversion for hydrogen-resistant martensitic steel design.
Carbon-supersaturated nanocrystalline hypereutectoid steels with a tensile strength of 6.35 GPa were produced from severely cold-drawn pearlite. The nanocrystalline material undergoes softening upon annealing at temperatures between 200...
moreCarbon-supersaturated nanocrystalline hypereutectoid steels with a tensile strength of 6.35 GPa were produced from severely cold-drawn pearlite. The nanocrystalline material undergoes softening upon annealing at temperatures between 200 and 450 C. The ductility in terms of elon-gation to failure exhibits a non-monotonic dependence on temperature. Here, the microstructural mechanisms responsible for changes in the mechan-ical properties were studied using transmission electron microscopy (TEM), TEM-based automated scanning nanobeam diffraction and atom probe tomography (APT). TEM and APT investigations of the nanocrystalline hypereutectoid steel show subgrain coarsening upon annealing, which leads to strength reduction following a Hall–Petch law. APT analyzes of the Mn distribution near subgrain boundaries and in the cementite give strong evidence of capillary-driven subgrain coarsening occurring through subgrain boundary migration. The pronounced deterioration of ductility after ann...
Abstract The ferritic rolling strategy allows for the production of two different hot strip grades, a" soft" and a" hard" hot strip. The" soft" hot strip is...
moreAbstract The ferritic rolling strategy allows for the production of two different hot strip grades, a" soft" and a" hard" hot strip. The" soft" hot strip is rolled in the upper ferrite region and a sufficiently high coiling temperature ensures direct recrystallisation in the coil. The" hard" hot strip is rolled at relatively lower temperatures in the ferrite temperature region and exhibits a strained microstructure with a desirable rolling texture. Furthermore, these ferritic rolled hot strips can be used as initial strip for subsequent cold rolling. The current investigation ...
Abstract Duplex stainless steels (DSSs) are based on the Fe-Cr-Ni system and formed by ferrite (30-70%) and austenite. They have high tensile strength, good toughness and weldability and excellent corrosion resistance including...
moreAbstract Duplex stainless steels (DSSs) are based on the Fe-Cr-Ni system and formed by ferrite (30-70%) and austenite. They have high tensile strength, good toughness and weldability and excellent corrosion resistance including stress-corrosion cracking and resistance to localized corrosion. The increase of the raw materials of the last years, there has been a motivation to develop new stainless steels with lower contents of nickel and molybdenum. Lean duplex stainless steels (LDSSs) are almost Mo free and nickel content ...
... Sci., 1984, 19, 1799 [5] Luton, MJ, Sellars, СМ.: Acta metall., 1969, 17, ЮЗЗ [6] Jonas, JJ,McQueen, HJ: Treatise in Materials Science and Technology, ed. RJ Arsenault, Academic Press, New York, 1975, 6_, 393 [7] Bromley, R., Sellars,...
more... Sci., 1984, 19, 1799 [5] Luton, MJ, Sellars, СМ.: Acta metall., 1969, 17, ЮЗЗ [6] Jonas, JJ,McQueen, HJ: Treatise in Materials Science and Technology, ed. RJ Arsenault, Academic Press, New York, 1975, 6_, 393 [7] Bromley, R., Sellars, СМ.: Proc. 3rd Int. Conf. ...
We present a design strategy for a new type of age hardenable ultrahigh strength TRIP-assisted steels with a good tensile elongation. The alloys have a low carbon content (below 0.02 mass% C), 9–15 mass% Mn and, in order to reduce costs,...
moreWe present a design strategy for a new type of age hardenable ultrahigh strength TRIP-assisted steels with a good tensile elongation. The alloys have a low carbon content (below 0.02 mass% C), 9–15 mass% Mn and, in order to reduce costs, only minor additions of Ni, Al, Ti, and Mo (of the order of 1–2 mass%). After quenching the microstructure of these steels comprises martensite and different amounts of retained austenite. During age hardening the strength and ductility can be increased simultaneously: The strength is increased by the ...
Duplex stainless steels (DSSs) are based on the Fe-Cr-Ni system and consist of ferrite (30-70%) and austenite. DSSs have shown an excellent combination of resistance to general and localized corrosion, stress corrosion cracking, high...
moreDuplex stainless steels (DSSs) are based on the Fe-Cr-Ni system and consist of ferrite (30-70%) and austenite. DSSs have shown an excellent combination of resistance to general and localized corrosion, stress corrosion cracking, high strength and low cost due to reduced contents of Ni and Mo [1-3]. DSSs are used in oil, gas, paper, desalination and petrochemical industries. The main process steps in the industrial manufacturing of duplex stainless steel sheets are continuous casting, slab reheating, hot rolling, coiling, hot band ...
A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution....
moreA precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected.
7. Conclusions We present atom probe tomography results of a precipitation-hardened Mn-based maraging steel (9 Mn, 1.9 Ni, 0.6 Mo, 1.1 Ti, 0.33 Al; in at.%). The alloy is characterized by the surprising effect that both, strength and...
more7. Conclusions We present atom probe tomography results of a precipitation-hardened Mn-based maraging steel (9 Mn, 1.9 Ni, 0.6 Mo, 1.1 Ti, 0.33 Al; in at.%). The alloy is characterized by the surprising effect that both, strength and total elongation increase upon aging. The material reveals a high ultimate tensile strength (UTS) up to 1 GPa and good ductility (total elongation (TE) of up to 15% in a tensile test) depending on aging conditions. We map the evolution of the precipitates after 450 C aging treatment using atom probe ...