An improved thermodynamic modeling of the Fe–Cr system down to zero kelvin coupled with key experiments

Xiong, Wei; Hedström, Peter; Selleby, Malin; Odqvist, Joakim; Thuvander, Mattias; Chen, Qing

doi:10.1016/j.calphad.2011.05.002

Cited by 158 publications

(129 citation statements)

References 44 publications

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“…13, and references therein). Direct observations from three dimensional APT investigations have also demonstrated the transition of the phase separation mechanism from nucleation-and-growth to spinodal decomposition in the composition range of 25-35% Cr at 773 K. 13 Whereas the spinodal nature of the decomposition process have been questioned for similar systems, e.g., Fe-Cr-Co, 14 based on the development of the SANS invariant during ageing, similar studies of the Fe-Cr binary system show no such indications. 6 During the spinodal decomposition, a characteristic interconnected structure with nano-scale modulations of the composition forms.…”

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confidence: 99%

“…This composition is within the spinodal and has been shown previously to result in the characteristic interconnected structure during ageing at the intended temperatures. 13 The material was cut into approximately 1.5 mm thick pieces with a 10 Â 10 mm square crosssection and subsequently ground and polished to remove surface oxides.…”

mentioning

confidence: 99%

“…7,19 The binary Fe-Cr alloy was produced by vacuum arc melting (see Ref. 13 for more details on material preparation), followed by solution treatment at 1373 K for 2 h under pure argon and a final quench in brine. The final alloy composition (in wt.…”

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confidence: 99%

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Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Hörnqvist

Thuvander

Steuwer

et al. 2015

Applied Physics Letters

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In-situ, time-resolved small-angle neutron scattering (SANS) investigations of the early stages of the spinodal decomposition process in Fe-35Cr were performed at 773 and 798 K. The kinetics of the decomposition, both in terms of characteristic distance and peak intensity, followed a power-law behaviour from the start of the heat treatment (a 0 ¼ 0.10-0.11 and a 00 ¼ 0.67-0.86). Furthermore, the method allows tracking of the high-Q slope, which is a sensitive measure of the early stages of decomposition. Ex-situ SANS and atom probe tomography were used to verify the results from the in-situ investigations. Finally, the in-situ measurement of the evolution of the characteristic distance at 773 K was compared with the predictions from the Cahn-Hilliard-Cook model, which showed good agreement with the experimental data (a 0 ¼ 0.12-0.20 depending on the assumed mobility). Spinodal decomposition of the bcc phase in Fe-Cr alloys into an Fe-rich and a Cr-rich phase is a widely studied phenomenon. The reason is two-fold: First, the system is the basis of the industrially important stainless steel family, where the decomposition of the bcc phase in ferritic, duplex and to some extent martensitic and d-ferrite containing austenitic grades, is partially responsible for degradation of the mechanical properties over time during elevated temperature exposure in service. Second, the Fe-Cr system is ideal to study the fundamentals of the spinodal decomposition process, since it offers a combination of a wide miscibility gap, a rather wide temperature range where the kinetics of the decomposition is suitable for practical measurements and minor coherency strains.The decomposition process in Fe-Cr is typically investigated by transmission electron microscopy (TEM), 1 M€ ossbauer spectroscopy, 2,3 atom probe tomography (APT), 4,5 or smallangle neutron scattering (SANS). [6][7][8] While each technique has its specific advantages, only SANS readily offers the possibility to perform time-resolved in-situ measurements at elevated temperatures. However, so far only very few investigations have taken advantage of this possibility of direct continuous tracking of the kinetics without any specimen-to-specimen variations in composition, starting structure, or isothermal temperature. For the Fe-Cr(-Ni) system, there are only two readily available reports of in-situ SANS experiments, 9,10 although other systems have been investigated more recently, e.g., Fe-Co-Mo. 11 In Refs. 9 and 10, acquisition times of several hours were used, which resulted in poor temporal resolution. Furusaka et al. 12 used in-situ SANS to investigate the critical scattering of Fe-Cr alloys in the vicinity of the Curie temperature, but the subsequent investigations of aged alloys were performed ex-situ.The existence and location of the spinodal in the binary Fe-Cr system are today rather well described, both from thermodynamic modelling and experiments (see, e.g., Ref. 13, and references therein). Direct observations from three dimensional APT investigations have also...

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confidence: 99%

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Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Hörnqvist

Thuvander

Steuwer

et al. 2015

Applied Physics Letters

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“…Meanwhile, more efforts should be made on bridging the current DFT-based atomistic models and CALPHAD method by extending their temperature scales. 115 A recent work on the Fe-Cr system 22 demonstrated that the CALPHAD models extended to 0 K will garner valuable insights into anomalous phenomenon, i.e., negative enthalpy of mixing on Fe-rich side, found in enthalpy of formation generated by DFT calculations. 116 Expending the impact of the structure-property model development, genomic databases of mechanistic constitutive laws for mechanical FEA should be initiated.…”

Section: Summary: Cybermaterials Innovation Based On Materials Genomementioning

confidence: 99%

“…This is now considered as a routine method to perform physically sound thermodynamic modelling, which can sometimes circumvent the restriction of calorimetry (e.g., radiative alloy systems), 19,20 and assist in determining reliable experimental data sets. 19,[21][22][23] At present, there are many commercial software packages available based on the CALPHAD technique, e.g., Thermo-Calc, Pandat, FactSage, MTDATA. 24,25 However, not until the release of the DICTRA (diffusion controlled transformations) package by the Thermo-Calc software company in early 90s 26,27 for diffusion kinetic modelling, did the CALPHAD approach start to demonstrate its capability of handling sophisticated processstructure modelling.…”

Section: Materials By Design: Design Enginementioning

confidence: 99%

Cybermaterials: materials by design and accelerated insertion of materials

Xiong

Olson

2016

npj Comput Mater

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Cybermaterials innovation entails an integration of Materials by Design and accelerated insertion of materials (AIM), which transfers studio ideation into industrial manufacturing. By assembling a hierarchical architecture of integrated computational materials design (ICMD) based on materials genomic fundamental databases, the ICMD mechanistic design models accelerate innovation. We here review progress in the development of linkage models of the process-structure-property-performance paradigm, as well as related design accelerating tools. Extending the materials development capability based on phase-level structural control requires more fundamental investment at the level of the Materials Genome, with focus on improving applicable parametric design models and constructing high-quality databases. Future opportunities in materials genomic research serving both Materials by Design and AIM are addressed. BACKGROUND: ICMD BLUEPRINTThe far-reaching multi-agency enterprise, Materials Genome Initiative (MGI), 1,2 highlights computational materials design techniques grounded in fundamental databases, which can support an ambition of decreasing the full development cycle of new materials from the present 10-20 years to ⩽ 5 years. As a subfield of the broader field of integrated computational materials engineering (ICME), which includes modelling of existing materials, 3,4 the MGI centres on design of new materials and their accelerated qualification through the inherent predictability of designed systems. Creation of the infrastructure of this technology has been a global activity as summarised in a recent series of viewpoint papers on materials genomics. 5-10 Particularly notable has been the design work of Bhadeshia 8 at the University of Cambridge and his former students including Harada 11,12 and Reed. 13 The highest achievements of full cycle compression have been demonstrated in US research, which will be the focus of this paper.In the development of applied engineering materials design powered by fundamental thermodynamic and kinetic genomic databases, a hierarchical infrastructure called ICMD presents a proven scenario of materials genomic design for accelerated engineering innovation. As indicated in Figure 1, the backbone of the ICMD infrastructure is composed of Materials by Design and accelerated insertion of materials (AIM) techniques. The application of both techniques spans the entire course of materials innovation, which can be divided into three phases: concept implementation, materials and processing design, and material qualification. The quality of the materials innovation is determined by the mechanistic models applied in the ICMD framework, which follow the universal process-structure-property-performance paradigm in materials science. 14 In Materials by Design, both process-structure and structure-property models are evaluated and refined to maximise the model-predictability grounded in the Materials Genome, which is powered by fundamental research on

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3D Analysis of Phase Separation in Ferritic Stainless Steels

Odqvist

Zhou

Hedström

et al. 2013

1^stInternational Conference on 3D Materials Science

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The embrittlement of ferritic stainless steels during low temperature aging is attributed to the phase separation with Fe and Cr demixing. The small scale of the decomposed structure with only minor compositional fluctuations and short distances between the enriched and depleted regions has been a challenge for quite some time. A wide selection of experimental and modeling tools have been used to quantify these types of structures. These analyses often focus on rather late stages of decomposition where the mechanical properties are already seriously affected. The recent advance in 3D tools like phase-field and atom probe tomography have created a need for good quantitative procedures of evaluating the structure and also to link results from the continuum approach to the individual atom measurements. This work aims at addressing this need.

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An improved thermodynamic modeling of the Fe–Cr system down to zero kelvin coupled with key experiments

Cited by 158 publications

References 44 publications

Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Cybermaterials: materials by design and accelerated insertion of materials

3D Analysis of Phase Separation in Ferritic Stainless Steels

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