Critical Evaluation and Optimization of the Fe-N, Mn-N and Fe-Mn-N Systems

You, Zhimin; Paek, Min-Kyu; Jung, In‐Ho

doi:10.1007/s11669-018-0666-8

Cited by 16 publications

(18 citation statements)

References 85 publications

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“…Somewhat before our experimental study at 13 GPa, Breton et al [ 24 ] published an alternative P–T projection of phase equilibria in the Fe–N system covering the pressure range of 15–60 GPa and temperature range of 300–1600 K. The derived P – T projection shows an invariant point involving γ′-Fe 4 N at 41 GPa and 1000 K and implies thermodynamic stability (or re-appearance) of the γ′-Fe 4 N up to 56 GPa at 300 K, apparently contradicting experimental results at high pressure [ 23 , 32 ] and currently accepted thermodynamic models of the system at atmospheric pressure [ 7 , 8 ].…”

Section: Introductionmentioning

confidence: 70%

“…This in turn means that Fe nitrides are generally metastable with respect to decomposition into Fe and N 2 at the nitriding temperatures. Currently accepted thermodynamic databases [ 7 , 8 ] represent the metastable phase equilibria in the Fe–N system with a topology similar to that shown in Figure 1 . It is generally accepted that the γ′ phase transforms to

by a congruent reaction

(c 1 ) and that there are at least two more eutectoid reactions,

(e 1 ) and

(e 2 ).…”

Section: Introductionmentioning

confidence: 99%

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Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N System

et al. 2021

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Although the general instability of the iron nitride γ′-Fe4N with respect to other phases at high pressure is well established, the actual type of phase transitions and equilibrium conditions of their occurrence are, as of yet, poorly investigated. In the present study, samples of γ′-Fe4N and mixtures of α Fe and γ′-Fe4N powders have been heat-treated at temperatures between 250 and 1000 °C and pressures between 2 and 8 GPa in a multi-anvil press, in order to investigate phase equilibria involving the γ′ phase. Samples heat-treated at high-pressure conditions, were quenched, subsequently decompressed, and then analysed ex situ. Microstructure analysis is used to derive implications on the phase transformations during the heat treatments. Further, it is confirmed that the Fe–N phases in the target composition range are quenchable. Thus, phase proportions and chemical composition of the phases, determined from ex situ X-ray diffraction data, allowed conclusions about the phase equilibria at high-pressure conditions. Further, evidence for the low-temperature eutectoid decomposition γ′→α+ε′ is presented for the first time. From the observed equilibria, a P–T projection of the univariant equilibria in the Fe-rich portion of the Fe–N system is derived, which features a quadruple point at 5 GPa and 375 °C, above which γ′-Fe4N is thermodynamically unstable. The experimental work is supplemented by ab initio calculations in order to discuss the relative phase stability and energy landscape in the Fe–N system, from the ground state to conditions accessible in the multi-anvil experiments. It is concluded that γ′-Fe4N, which is unstable with respect to other phases at 0 K (at any pressure), has to be entropically stabilised in order to occur as stable phase system. In view of the frequently reported metastable retention of the γ′ phase during room temperature compression experiments, energetic and kinetic aspects of the polymorphic transition γ′⇌ε′ are discussed.

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Section: Introductionmentioning

confidence: 70%

by a congruent reaction

(c 1 ) and that there are at least two more eutectoid reactions,

(e 1 ) and

(e 2 ).…”

Section: Introductionmentioning

confidence: 99%

Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N System

et al. 2021

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“…Conversely, the energy required to reverse the direction of N migration will be greater due to this same factor. Additionally, even as MnN decomposes to Mn 3 N 2 as seen in HAADF-STEM, the calculated Gibbs free energy is −212.6 kJ/mol for the reaction shown in eq , , indicating even as N is lost, the remaining Ta will preferentially form TaN over the reverse reaction. …”

Section: Discussionmentioning

confidence: 99%

Nitrogen-Based Magneto-ionic Manipulation of Exchange Bias in CoFe/MnN Heterostructures

et al. 2023

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Electric field control of the exchange bias effect across ferromagnet/antiferromagnet (FM/AF) interfaces has offered exciting potentials for low-energy-dissipation spintronics. In particular, the solid-state magneto-ionic means is highly appealing as it may allow reconfigurable electronics by transforming the all-important FM/AF interfaces through ionic migration. In this work, we demonstrate an approach that combines the chemically induced magneto-ionic effect with the electric field driving of nitrogen in the Ta/Co0.7Fe0.3/MnN/Ta structure to electrically manipulate exchange bias. Upon field-cooling the heterostructure, ionic diffusion of nitrogen from MnN into the Ta layers occurs. A significant exchange bias of 618 Oe at 300 K and 1484 Oe at 10 K is observed, which can be further enhanced after a voltage conditioning by 5 and 19%, respectively. This enhancement can be reversed by voltage conditioning with an opposite polarity. Nitrogen migration within the MnN layer and into the Ta capping layer cause the enhancement in exchange bias, which is observed in polarized neutron reflectometry studies. These results demonstrate an effective nitrogen-ion based magneto-ionic manipulation of exchange bias in solid-state devices.

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“…The analysis of the equilibrium in the Fe-N system allows obtaining information regarding the phase composition of the nitrided layers obtained under strict conditions of temperature and nitrogen concentration in the furnace chamber atmosphere [ 1 , 2 , 3 , 4 , 5 ]. The adjustment of the nitrided layer phase composition can be set by altering the nitrogen potential of the atmospheres used: by maintaining it at the level of nitrogen solubility in a certain phase, one is able to control the phase composition of the layer [ 6 , 7 , 8 , 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

The Effects of Modifying the Activity of Nitriding Media by Diluting Ammonia with Nitrogen

et al. 2021

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This paper discusses the issue of the effects of modifying the activity of nitriding media by diluting ammonia with nitrogen and the concomitant variation in the degree of ammonia dissociation on the layer’s growth kinetics and their phase composition. To understand and quantify the effects of the variation in the main parameters that influence the layer growth kinetics, the experimental programming method was used and mathematical models of interactions between influence and kinetics parameters were obtained for two metallic materials: Fe-ARMCO and 34CrAlMo5 nitralloy steel. It was concluded that the nitriding operating temperature and the degree of nitrogen dilution of the ammonia have statistically significant influences on the kinetics of the nitrided layer. In the same context, it was analytically proved and experimentally confirmed that the ammonia degree dissociation from the gaseous ammonia-nitrogen mixture, along with the dilution degree of the medium with nitrogen, significantly influences the nitrogen potential of the gaseous mixture used for nitriding and thus the concentration of nitrogen in balance at the medium thermochemically processed metal product interface.

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Critical Evaluation and Optimization of the Fe-N, Mn-N and Fe-Mn-N Systems

Cited by 16 publications

References 85 publications

Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N System

Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N System

Nitrogen-Based Magneto-ionic Manipulation of Exchange Bias in CoFe/MnN Heterostructures

The Effects of Modifying the Activity of Nitriding Media by Diluting Ammonia with Nitrogen

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