A calorimetric study of precipitation in aluminum alloy 2219

Papazian, John M.

doi:10.1007/bf02655200

Cited by 160 publications

(37 citation statements)

References 19 publications

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“…in verification of industrial heat treatments, and in this case the application is sometimes termed DSC fingerprinting. 67,68 Another application is in assessing heat treatments that parts of materials that are inaccessible for recording of temperature history have undergone. An example of the latter is the study of heat affected zones in welds of heat treatable Al based alloys.…”

Section: -67mentioning

confidence: 99%

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

Starink¹

2004

International Materials Reviews

286

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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Section: -67mentioning

confidence: 99%

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

Starink¹

2004

International Materials Reviews

286

108

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“…Overlapping precipitation of θ'-type and S'-type particles, which often form in precipitationhardened 2024 alloys containing Mg additions, may be assumed to be the underlying cause for a double exothermic peak noticeable in DSC traces at temperatures between 530 K and 650 K. In practice, however, the interpretation of the double-peak behavior observed for AA2000-series alloys reported in the literature is not consistent. In the most recent report, DSC maxima observed for the AA2024 alloy at 543 K and 573 K, and a double peak recorded for the AA2324 alloy were ascribed to the development of the S1 and S2 phases [9]. Some previous experiments on the AA2024 and AA2618 alloys had also revealed a double peak in DSC traces for solution-treated samples; this double peak disappeared after preliminary ageing at 498 K/1h [3].…”

Section: Introductionmentioning

confidence: 89%

Precipitation Processes during Non-Isothermal Ageing of Fine-Grained 2024 Alloy

Kozieł¹,

Błaż²,

Włoch³

et al. 2016

Archives of Metallurgy and Materials

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PrecIPItatIon Processes durIng non-Isothermal ageIng of fIne-graIned 2024 alloyMechanical alloying and powder metallurgy procedures were used to manufacture very fine-grained bulk material made from chips of the 2024 aluminum alloy. Studies of solution treatment and precipitation hardening of as-received material were based on differential scanning calorimetry (DSC) tests and TEM/STEM/EDX structural observations. Structural observations complemented by literature data lead to the conclusion that in the case of highly refined structure of commercial 2024 alloys prepared by severe plastic deformation, typical multi-step G-P-B →θ" →θ' →θ precipitation mechanism accompanied with G-P-B →S" →S' →S precipitation sequences result in skipping the formation of metastable phases and direct growth of the stable phases. Exothermic effects on DSC characteristics, which are reported for precipitation sequences in commercial materials, were found to be reduced with increased milling time. Moreover, prolonged milling of 2024 chips was found to shift the exothermic peak to lower temperature with respect to the material produced by means of common metallurgy methods. This effect was concluded to result from preferred heterogeneous nucleation of particles at subboundaries and grain boundaries, enhanced by the boundary diffusion in highly refined structures.Transmission electron microscopy and diffraction pattern analysis revealed the development of very fine Al4C3 particles that grow due to the chemical reaction between the Al matrix and graphite flakes introduced as a process control agent during the preliminary milling of chips. Al4C3 nano-particles are formed at high temperatures, i.e. during hot extrusion and the subsequent solution treatment of the samples. Highly refined insoluble particles such as aluminum carbide particles and aluminum oxides were found to retard recrystallization and reduce recovery processes during solution treatment of preliminarily milled materials. Therefore, the as-extruded material composed of a milled part and chip residuals retained its initial bimodal structure in spite of solution heat treatment procedures. This points to a high structural stability of the investigated materials, which is commonly required for new technologies of high-strength Al-based materials production.

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“…Figure 3 shows DSC traces of unmilled and milled Al-4%Cu powders. The DSC trace of the unmilled powder contains a starting endothermic peak which corresponds to the dissolution of the Guinier-Preston (GP) zones formed during heating [14,15]. The exothermic peak starting from around 473 K is attributed to the precipitation of θ'(Al 2 Cu) phase [16].…”

Section: Structural and Morphological Characterizationsmentioning

confidence: 99%

X‐ray studies of structure defects in nanostructured Al‐4wt%Cu alloy

Khitouni

Daly

Kolsi

et al. 2006

Phys. Status Solidi (c)

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The process of nanocrystalline structure formation during mechanical milling was studied in Al-4wt%Cu alloy. X-ray patterns were analyzed to determine the crystallite size, the lattice strain, probability of the stacking faults and the lattice parameters. As a result, nanocrystalline powders have been synthesized with microstructure showing a mixture of highly strained crystallites. High level of lattice strain is achieved as a result of mechanical milling. This fact can reflect a significant increase in the numbers of defects created. SEM results show that welding of very small particles to the surface of big particles was occurred and the powder particles tend to form a matrix of randomly welded thin layers of highly deformed particles. The microstructure, observed by TEM, was composed of nanometric grains and the statistical average grain size is about 29 nm.

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A calorimetric study of precipitation in aluminum alloy 2219

Cited by 160 publications

References 19 publications

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

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

Precipitation Processes during Non-Isothermal Ageing of Fine-Grained 2024 Alloy

X‐ray studies of structure defects in nanostructured Al‐4wt%Cu alloy

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