Effect of external stress on the Fe–Cr phase separation in 15-5 PH and Fe–15Cr–5Ni alloys

The effect on Fe–Cr phase separation of a uniaxial stress during thermal ageing at 4251C is investigated on a Fe–15Cr–5Ni steel, a model alloy of commercial 15-5 PH steel. The applied stress is shown to accelerate the ageing kinetics, and influence the morphology of Cr rich domains. A dependence of the phase separation decomposition kinetics on the relative orientations of the load and the crystal local orientation has also been observed

An Experimental Assessment of the α + α’ Miscibility Gap in Fe-Cr

International audiencePhase separation in the Fe-Cr system has been studied experimentally. The upper limit of the miscibility gap and phase separation kinetics during the early stages of decomposition was studied using Vickers micro-hardness tests and atom probe tomography. The results indicate that the upper limit of the miscibility gap in current thermodynamic descriptions is overestimated, but it is necessary to further analyze the transition across the upper limit of the miscibility gap before drawing conclusions. This work demonstrates the efficient combination of micro-hardness measurements and atom probe tomography to investigate the miscibility gap in the Fe-Cr system

Nucleation and growth of carbo-nitride nanoparticles in α-Fe-based alloys and associated interfacial process

International audiencePrecipitation of nanoparticles from a supersaturated solid solution is important in understanding and controlling the formation of nanostructure, and as a result, many physical properties of materials, such as conductivity, mechanical, thermoelectric, and magnetic behavior of materials. In each case, the precipitation state, including size, density, chemical composition, spatial distribution, particle morphology, and volume fraction, of nanoparticles can all influence the properties of interest. In an effort to design nano/microstructures in steels, mainly for automotive applications, it is important to be able to describe the time evolution of the precipitation state, including both the nucleation and the growth processes. The present review is thus concerned with the homogenous precipitation of carbo-nitride nanoparticles in α-ferrite. The interfacial process, the time evolution of both carbon and nitrogen into precipitates, and the effects of supersaturation and spatial distribution are discussed and clarified. The involved mechanisms are discussed from a theoretical point of view; some major results are illustrated from newly developed experimental methods, and their relevance to topics of current interest is examined. At last, some major outstanding issues have been identified and avenues for further research suggested

An Experimental Assessment of the α + α’ Miscibility Gap in Fe-Cr

International audiencePhase separation in the Fe-Cr system has been studied experimentally. The upper limit of the miscibility gap and phase separation kinetics during the early stages of decomposition was studied using Vickers micro-hardness tests and atom probe tomography. The results indicate that the upper limit of the miscibility gap in current thermodynamic descriptions is overestimated, but it is necessary to further analyze the transition across the upper limit of the miscibility gap before drawing conclusions. This work demonstrates the efficient combination of micro-hardness measurements and atom probe tomography to investigate the miscibility gap in the Fe-Cr system

An Experimental Assessment of the α + α’ Miscibility Gap in Fe-Cr

International audiencePhase separation in the Fe-Cr system has been studied experimentally. The upper limit of the miscibility gap and phase separation kinetics during the early stages of decomposition was studied using Vickers micro-hardness tests and atom probe tomography. The results indicate that the upper limit of the miscibility gap in current thermodynamic descriptions is overestimated, but it is necessary to further analyze the transition across the upper limit of the miscibility gap before drawing conclusions. This work demonstrates the efficient combination of micro-hardness measurements and atom probe tomography to investigate the miscibility gap in the Fe-Cr system

Atom Probe Tomography I. Early Stages of Precipitation ofNbC andNbN in Ferritic Steels

The results reported in this paper give new information regarding the early stages of precipitation in model low niobium steels. It clearly appears that the kinetic paths for carbides and nitrides precipitation in the investigated model alloys are very different, more continuous in the case of carbides, and through GP zones formation in the case of nitrides

A direct evidence of solute interactions with a moving ferrite/austenite interface in a model Fe-C-Mn alloy

International audienceThe coupled-solute drag during ferrite growth in steels is widely discussed in the literature and remains still controversial since little direct evidences were adduced to support this effect. In this paper, from a correlative microscopy approach, a selected migrating ferrite/austenite interface in a model FeMnC alloy is quantitatively analysed by atom probe tomography and Energy Dispersive X-Ray Spectroscopy at the nanoscale. They show unambiguously a strong co-segregation of both carbon and manganese at the interface during ferrite growth at 680 °C. The obtained results support the coupled-solute drag effect as an operating mechanism during ferrite growth

A direct evidence of solute interactions with a moving ferrite/austenite interface in a model Fe-C-Mn alloy

The coupled-solute drag during ferrite growth in steels is widely discussed in the literature and remains still controversial since little direct evidences were adduced to support this effect. In this paper, from a correlative microscopy approach, a selected migrating ferrite/austenite interface in a model FeMnC alloy is quantitatively analysed by atom probe tomography and Energy Dispersive X-Ray Spectroscopy at the nanoscale. They show unambiguously a strong co-segregation of both carbon and manganese at the interface during ferrite growth at 680 °C. The obtained results support the coupled-solute drag effect as an operating mechanism during ferrite growth

Effect of external stress on the Fe–Cr phase separation in 15-5 PH and Fe–15Cr–5Ni alloys

International audienceThe effect on Fe–Cr phase separation of a uniaxial stress during thermal ageing at 4251C is investigated on a Fe–15Cr–5Ni steel, a model alloy of commercial 15-5 PH steel. The applied stress is shown to accelerate the ageing kinetics, and influence the morphology of Cr rich domains. A dependence of the phase separation decomposition kinetics on the relative orientations of the load and the crystal local orientation has also been observed

Carbon Atom Re-Distribution during Quenching and Partitioning

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