TEM characterization of the fine scale microstructure of a Roman ferrous nail

This paper describes the microstructure of a Roman ferrous nail through its observation by transmission electron microscopy. The morphologies of pearlitic colonies and ferritic grains are detailed and the relationship between pearlitic colonies and ferrite in Roman nails is explicitly demonstrated for the first time. Observations also confirm the presence of dislocations in ferritic grains and attest to the existence of very small carbide precipitates that have not been pointed out previously in standard archaeometric studies

Evolution of interfacial dislocation network during anisothermal high-temperature creep of a nickel-based superalloy

The effect of thermal cycling creep on the dislocation networks at the γ/γ′ interfaces in the MC2 superalloy is investigated. Tensile creep tests were performed under thermal cycling and isothermal conditions at low stress (80 MPa) and high temperature (1150 °C). In these conditions γ′ rafts may dissolve and reprecipitate during thermal cycling creep. The difference between the effects of isothermal and thermal cycling conditions on the γ/γ′ interface dislocation networks, characterized by transmission electron microscopy, is exposed, as well as their evolution during the cycle

Precipitation in original Duralumin A-U4G versus modern 2017A alloy

Precipitation in Duralumin, a historic quaternary alloy of the type: Al–Cu–Mg–Si, was never fully studied nor observed by current electron microscopy techniques. This article presents the full characterization and comparison of two alloys: a Duralumin (A-U4G) from the 1950s collected on a vintage aircraft and its modern equivalent: a 2017A alloy. The as-received and peak-aging states were analysed with DSC, SAXS and TEM advanced techniques. It is shown that old Duralumin and modern 2017A present a similar nanoprecipitation in the as-received state and behave similarly upon artificial aging. As opposed to what has been reported in the past, three types of precipitates participating in hardening were found upon aging: θ’-Al2Cu, Q’(Q)-AlCuMgSi and Ω-Al2Cu

Long-term thermal ageing of the 2219-T851 and the 2050-T84 Al-Cu alloys

International audienceIn this study, the influence of high temperature exposure on mechanical properties as well as on the microstructures of two Al-Cu alloys, has been investigated. Driven by an industrial will to use structural aluminium at higher temperature than usually stated, this work is focused on the characterization of the evolution of two commercial alloys, the 2219-T851 and the 2050-T84, induced by an ageing treatment of 1000 hours at 200°C. Careful TEM observations confirm the importance of the nanoscale precipitation and that the precipitate size and distribution strongly influence the mechanical properties of the studied alloys. Results unexpectedly show that the precipitates are more stable in time than the precipitates at this temperature. Regarding the mechanical properties related to ageing, it follows that the 2219-T851 alloy presents a reduced drop with time of its tensile test curves compared to the 2050-T84, thus a limited, and at least less pronounced, temperature dependence. For an industrial application on structural part, 2219-T851 alloy then appears to be a good candidate for long-term structural applications at intermediate temperatures

Elastic strain around needle-shaped particles embedded in Al matrix

International audiencePrecise measurements of strain fields around precipitates embedded in a crystalline matrix were performed, and simple but accurate models were deduced from the observations. The measurements were carried out in an aged aluminum alloy containing needle-shaped particles. The displacement and strain fields around rod-shaped and lath-shaped particles were obtained from high-resolution electron micrographs using geometric phase analysis. The measurements reveal that strain field of a rod-shaped particle is well described by the classical Eshelby analytical elastic solution. For the more complex case of lath precipitates, it is shown that the strain field in the matrix can be simply approximated by a dislocations dipole. The methods developed are generally applicable to the characterization of strain in nano-structured materials, including those with complex or unknown structures

Study of the evolution of two Al-Cu-(Li) alloys during thermal ageing

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Microstructure Changes Due to Heat Treatment and Their Effects on the Plasticity of Aluminium Alloys

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Long-term thermal ageing effects on Al-Cu alloys

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Étude d'un alliage d'aluminium pour l'aéronautique par les techniques avancées de microscopie électronique en transmission

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF