Development of Ni-free Mn-stabilised maraging steels using Fe2SiTi precipitates

Knowles, Alexander J.; Gong, Peng; Rahman, K.M.; Rainforth, W. M.; Dye, David; Galindo-Nava, E.I.

doi:10.1016/j.actamat.2019.05.034

Cited by 15 publications

(6 citation statements)

References 36 publications

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“…The alloy cost was calculated using the estimated cost by alloy addition (USD/wt.% per tonne) found in ref. 31 . Those values fluctuate considerably according to demand 32 and they are used here only for the sake of relative comparison.…”

Section: Methodsmentioning

confidence: 99%

A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation

Silva

Filho

et al. 2022

Nat Commun

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The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of second-phase precipitates with sizes in the nanometre range is particularly effective for achieving ultra-high strength. Here, we propose an alternative segregation-based strategy for sustainable steels, free of critical elements, which are rendered ultrastrong by second-phase nano-precipitation. We increase the Mn-content in a supersaturated, metastable Fe-Mn solid solution to trigger compositional fluctuations and nano-segregation in the bulk. These fluctuations act as precursors for the nucleation of an unexpected α-Mn phase, which impedes dislocation motion, thus enabling precipitation strengthening. Our steel outperforms most common commercial alloys, yet it is free of critical elements, making it a new platform for sustainable alloy design.

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Section: Methodsmentioning

confidence: 99%

A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation

Silva

Filho

et al. 2022

Nat Commun

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“…Such optimal microstructural combination is very difficult to achieve in intermetallic-forming steels; we have shown that times to reach peak hardness for typical intermetallics present in maraging steels, e.g. Ni3Ti, NiAl, and Cu, are at least one order of magnitude shorter, 1h-100h, than the times required to form 30% of reverted austenite (>100h) when ageing between 450 o C-550 o C [42]. This conflicting issue demands for exploring other alloy compositions that can accelerate the kinetics of austenite and match it with fine precipitation.…”

Section: Introductionmentioning

confidence: 97%

“…Although these steels display excellent combinations of very high-strength and toughness, whilst at the same time being easy to process requiring a single ageing step, the main two limitations in their widespread applications have been their very high costs and virtually no ductility at their peak-aged condition. For the former, it is possible to replace expensive additions of Ni and Co with ~10 wt% of Mn to stabilise lath martensite [42]. As for increasing the ductility, a viable solution has been to promote the reversion of (lath-shaped) austenite; we have shown that at least 30% of austenite is needed to increase the steel's ductility to ~20% [], [30].…”

Section: Introductionmentioning

confidence: 99%

Effect of ageing on the microstructural evolution in a new design of maraging steels with carbon

et al. 2020

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A new maraging steel, based on carbide precipitation, is described. Two alloys were designed namely Fe-10Mn-0.25C-2Cr-1Mo wt% (2CrMo) and Fe-10Mn-0.25C-1Cr-2Mo wt% (Cr2Mo). These compositions were chosen to achieve ultra-high strength and high tensile elongation; the former and latter are promoted through the simulatenous precipitation of Cr-and Mo-rich carbides and Mn-rich reverted austenite. The alloys were manufactured through the standard melting, casting and hot working route. Following a solution treatment at 870 °C and quench, which gave a fully martensitic structure, the alloys were aged for various times at 510 °C. The microstructure and tensile properties were investigated in detail as a function of ageing time.The microstructure observed was dominated by micron scale and nanometer scale Mn segregation which determined the local Ac3 temperature. Austenite reversion occurred in both alloys, peaking at 16h in both cases. In the 2CrMo alloy, the reverted austenite was mainly globular in morphology due the Ac3 temperature being lower than the ageing temperature, but was acicular in the Cr2Mo with Ac3 similar to the ageing temperature of 510 °C. Moreover, acicular austenite was promoted by Mn segregation at martensite lath boundaries in Cr2Mo.In the 2CrMo steel, carbide precipitation (M3C and M7C3) occurred during heating to the ageing temperature, but the carbides gradually dissolved with further ageing. In contrast, in the Cr2Mo alloy, precipitation of carbides (M7C3 and M2C) occurred during ageing, the volume fraction of which increased with ageing time. In both alloys a TRIP effect was observed, but the extent of this was greater for the Cr2Mo alloy. The complex microstructure obtained after 16h led to an excellent combination of strength of 1.3GPa and elongation of 18%. Physics-based models for the microstructure in martensite, precipitation kinetics, as well as for TRIP in austenite were employed to explain and predict the individual strengthtening contributions of the microstructure to the total strength, confirming that the maximum strength-elongation relationship found after 16h is due to an optimal combination of a slightly overaged -but still strong-martensite and 30% of reverted austenite, for increased work hardening and ductility.

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“…The second-generation advanced high-strength steels (2nd AHSS), mainly including high-Mn twinning-induced plasticity (TWIP) steels and high-Mn TRIP steels, possesses outstanding strength and remarkable ductility [ 2 ]. The improvement of ductility is mainly based on the TWIP or TRIP effect [ 1 , 5 , 6 ], and the improvement of strength is mainly ascribed to the formation of precipitates [ 4 , 7 ] or grain refinement [ 8 , 9 ]. Numerous studies have demonstrated that the addition of alloying elements such as Mo, Nb, and V can enhance their strength or ductility [ 10 , 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous Multi-Phase Grains Improving the Strength-Ductility Balance in Warm-Rolled Fe-18Mn-3Ti Steel

Li,

Liu,

Xia

et al. 2024

Materials

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The thermal properties, microstructure, and mechanical properties of Fe-18Mn-3Ti (wt%) were investigated, focusing on the effects of different heat-treatment processes. Results revealed that the 450 °C warm-rolling sample (450 WR) exhibited promising mechanical properties. Specifically, this sample displayed a yield strength of 988 MPa, an ultimate tensile strength of 1052 MPa, and total elongation of 15.49%. Consequently, a favorable strength-ductility balance was achieved. The strain-hardening ability surpassed that of the cold rolling sample (CR). Microstructure analysis indicated the simultaneous occurrence of dynamic equilibrium between grain deformation and re-crystallization because of the co-influence of thermal and strain in the warm rolling process. This desirable mechanical property was attributed to the presence of a multi-phase (α-martensite, austenite, and ε-martensite) and heterogeneous microstructure. The improvement of ultimate tensile strength was based on grain refinement, grain co-deformation, and the transformation-induced plasticity (TRIP) effect in the early stage of plastic deformation (stage Ⅰ). The improvement of ultimate elongation (TEL) was ascribed to the TRIP effect in the middle stage of plastic deformation (stage Ⅱ).

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Development of Ni-free Mn-stabilised maraging steels using Fe2SiTi precipitates

Abstract: This is a repository copy of Development of Ni-free Mn-stabilised maraging steels using Fe2SiTi precipitates.

Cited by 15 publications

References 36 publications

A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation

A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation

Effect of ageing on the microstructural evolution in a new design of maraging steels with carbon

Heterogeneous Multi-Phase Grains Improving the Strength-Ductility Balance in Warm-Rolled Fe-18Mn-3Ti Steel

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