Effect of concentration gradients on nanostructure development during primary crystallization of soft-magnetic iron-based amorphous alloys and its modelling

Yavari, A.R.; Negri, D.

doi:10.1016/s0965-9773(98)00047-6

Cited by 38 publications

(25 citation statements)

References 18 publications

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“…In fact, the blocking of the growth of the nanocrystals can be ascribed to the pile up of atoms non-soluble in -Fe grains and with a very slow diffusivity in the amorphous matrix [18], Nb in the studied alloy. [19].…”

Section: Theoretical Modelsmentioning

confidence: 93%

On the isothermal kinetics analysis of transformations in metastable systems: combined use of isothermal and non-isothermal calorimetry

Blázquez

Millán

Conde

et al. 2007

Philosophical Magazine

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1On the isothermal kinetics analysis of transformations in metastable systems. A combined use of isothermal and non-isothermal calorimetry. A procedure to optimize the isothermal calorimetric data of very slow transformation processes of metastable systems is proposed. The method uses an experimental baseline to identify the transitory effects due to the equipment. Moreover, the combined use of isothermal and non-isothermal results is shown to be effective to overcome the intrinsic problems of low signal and signal drift for such processes. The procedure has been applied to the analysis of the nanocrystallization kinetics of the Fe 60 Co 18 Nb 6 B 16 alloy at different devitrification stages. Based on microstructural observations, an instantaneous growth approach was assumed and a phenomenological expression of the dependence of the nucleation frequency with both the transformed fraction and the temperature was obtained.

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Section: Theoretical Modelsmentioning

confidence: 93%

On the isothermal kinetics analysis of transformations in metastable systems: combined use of isothermal and non-isothermal calorimetry

Blázquez

Millán

Conde

et al. 2007

Philosophical Magazine

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“…The emphasis will be on models for precipitation, devitrivication, and recrystallisation reactions which have either been recently derived or have recently attracted increased attention, and which have been reported to be able to deal with deviations from JMAK kinetics. The model by Woldt 200 considers recrystallisation, the models by Yavari and Negri 174 and Gangopadhyay et al 201 consider nanocrystallisation during devitrivication, Kelton's model 202,203 considers transformations that involve coupled fluxes of interfacial attachment and long-range diffusion, the mean field model considers precipitation, and the work by Starink and Zahra 170 describes a kinetic equation that can be valid for a range of reaction types.…”

mentioning

confidence: 99%

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

Starink¹

2004

International Materials Reviews

287

108

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Differential scanning calorimetry (DSC) and isothermal calorimetry have been applied extensively to the analysis of light metals, especially Al based alloys. Isothermal calorimetry and differential scanning calorimetry are used for analysis of solid state reactions, such as precipitation, homogenisation, devitrivication and recrystallisation; and solid-liquid reactions, such as incipient melting and solidification, are studied by differential scanning calorimetry. In producing repeatable calorimetry data on Al alloys, sample preparation, reproducibility and baseline drift need to be considered in detail. Calorimetry can be used effectively to study the different solid state reactions and solid-liquid reactions that occur during the main processing steps of Al based alloys (solidification, homogenisation, precipitation). Also, devitrivication of amorphous and ultrafine grained Al based powders and flakes can be studied effectively. Quantitative analysis of the kinetics of reactions is assessed through reviewing the interrelation between activation energy analysis methods, equivalent time approaches, impingement parameter approaches, mean field models for precipitation, the Johnson-Mehl-Avrami-Kolmogorov model, as well as novel models which have not yet found application in calorimetry. Differential scanning calorimetry has occasionally been used in attempts to measure the volume fractions of phases present in Al based alloys, and attempts at determining volume fractions of intermetallic phases in commercial alloys and amounts of devitrified phase in glasses are reviewed. The requirements for the validity of these quantitative applications are also reviewed.Keywords: Differential scanning calorimetry, Precipitation, Aluminium, Modelling, Transformation IMR/419 IntroductionCalorimetry is an analysis technique that is part of a group of techniques collectively known as thermal analysis methods. In its broadest sense, thermal analysis refers to the measurement of changes in properties of substances under a controlled temperature program. Thermal analysis techniques can be classified according to the type of temperature program that the sample is subjected to and the measured (output) signal. The most commonly used temperature programs are either isothermal hold or heating (scanning) at constant rate, while more recently, temperature modulated scanning and reaction controlled heating have also found application. The signals measured in thermal analysis can include heat flows, temperature changes, mass, evolved gasses, length changes, elastic modulus, and many other properties that characterise properties or reactions of interest. Calorimetry refers to thermal analysis methods that measure the heat evolution from a sample under a controlled temperature program. The two most often applied calorimetry techniques are isothermal calorimetry and differential scanning calorimetry (DSC), which, as the name suggests, is by definition non-isothermal (i.e. a temperature scan). Apart from the more common applications to polymers,...

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“…The amorphous and nanocrystalline total intensity contributions, shown in Fig. 2 (a) were obtained by deconvolution [10] of the first amorphous halo and the two most intense ((111) and (200)) fcc-Al peaks after background subtraction. The Lorentzian function fits were chosen for matching both amorphous halo and broadened fcc-Al peaks according to the best agreement with experimental data.…”

Section: Methods Assumptions and Proceduresmentioning

confidence: 99%

“…The apparent activation energies of the second crystallization stage are in the range from 11100 to 43900 K ( Table 5. For better understanding of kinetics of the second crystallization stage the samples of two amorphous alloys Al 90 Y 10 and Al 86 Ni 6 Co 2 Gd 6 have been annealed at temperatures somewhat lower then T ons2 to observe two crystallization stages in one experiment. As can be seen in Fig.…”

Section: Activity 23 Determination Of the Parameters Of Nanocompositmentioning

confidence: 99%

Development of High Strength Thermally Stable Al-based Alloys with Nanocomposite Structure

Maslov¹

2010

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)05-02-2010 REPORT TYPE Final Report DATES COVERED (From -To)01-Dec-06 -11-Jun-10 TITLE AND SUBTITLE PERFORMING ORGANIZATION REPORT NUMBERN/A SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)EOARD Unit 4515 BOX 14 APO AE 09421 SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S)STCU 06-8005 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTThis report results from a contract tasking Institute for Metal Physics, NAS of Ukraine as follows: The demands on materials set by aerospace and aircraft manufacturers include the development of alloys possessing high strength-to-weight ratios and capable to withstand high temperature exposures during service. One of the promising classes of materials which may meet these requirements are Al-based alloys with nanocomposite structures formed by partial crystallization of amorphous precursors the strength of which may exceed 1500 MPa. Solution of the problems concerning alloys chemistry and ability to tailor of certain microstructures is of prime importance for the development of new nanostructured materials. The goals of the project are to perform the systematic experimental studies of the effects of alloy composition and thermal prehistory on glassforming ability, thermal stability, crystallization behaviour and mechanical properties of a series binary, ternary and multicomponent Al-based alloys alloyed by transition metals and rare earths as well as to elaborate appropriate theoretical models of nanocrystallization processes. The main factors responsible for nanoscale microstructure formation will be determined from comparison of the experimental data with the model predictions.As a result a series of new Al-based alloys with nanocomposite structure with improved mechanical properties and enhanced thermal stability will be developed and the fundamental basis for the nanostructured alloys design will be created. SUBJECT TERMS

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Effect of concentration gradients on nanostructure development during primary crystallization of soft-magnetic iron-based amorphous alloys and its modelling

Cited by 38 publications

References 18 publications

On the isothermal kinetics analysis of transformations in metastable systems: combined use of isothermal and non-isothermal calorimetry

On the isothermal kinetics analysis of transformations in metastable systems: combined use of isothermal and non-isothermal calorimetry

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

Development of High Strength Thermally Stable Al-based Alloys with Nanocomposite Structure

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