On the long-term aging of S-phase in aluminum alloy 2618A (original) (raw)
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Recent advances in ageing of 7xxx series aluminum alloys: A physical metallurgy perspective
Journal of Alloys and Compounds, 2018
Al-Zn-Mg-Cu alloys (7xxx series Al alloys) are extensively used for their superior mechanical and corrosion performance. These properties are microstructure-sensitive and highly dependent on the formation, growth and coarsening of precipitates. To date, a wide variety of ageing procedures have been developed to tailor the evolved microstructures so as to yield a good combination of mechanical capacity and corrosion resistance of 7xxx series Al alloys. Among these methods, isothermal ageing, multi-stage ageing, non-isothermal ageing, retrogression and re-ageing (RRA), and stress ageing (i.e. creep ageing) are the most significant. In the present review, all of these approaches are comprehensively introduced and their potential effects on the microstructure and properties of Al-Zn-Mg-Cu alloys are fully reviewed. Also, recent advances and future prospect in this field are addressed. Keywords Ageing, precipitation hardening, creep ageing, non-isothermal ageing, retrogression and reageing, Al-Zn-Mg-Cu alloys 3xxx Al-Mn alloys 3xxx Al-Si + Cu and/or Mg 4xxx Al-Si alloys 4xxx Al-Si 5xxx Al-Mg alloys 5xxx Al-Mg 6xxx Al-Mg-Si alloys 6xxx Unused series 7xxx Al-Zn-Mg-Cu alloys 7xxx Al-Zn-Mg-Cu 8xxx Al+ other elements 8xxx Al-Sn
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Materials
Aluminum alloys such as AA2024 are popular in the automotive and aircraft industries. The application of artificial aging significantly improves their mechanical properties by precipitation hardening. However, commercial alloys very often contain different amounts of elements such as Si and Fe that make the evolution of the microstructure harder to control. Large intermetallic particles can influence the overall results of heat treatment and cause deterioration of material properties. The authors decided to examine changes in the microstructure of three commercial 2024 alloys with varying chemical compositions by applying three different types of aging treatments. The results show considerable differences in the amount, size and morphologies of the precipitates. Second-phase Al2Cu and Al2CuMg precipitates were identified in one of the alloys. Other interesting types of multiphase particles were discovered in alloys with higher Si contents. The results show that even small variations...
IFMohamed (SLee)_MMTA-2015-Aging behavior of al 6061 alloy processed by hpt and subsequent aging.pdf
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EFFECT OF SECONDARY AGING of EN AC 43200 ALUMINUM ALLOY to MECHANICAL PROPERTIES
International Journal of Materials Engineering, 2020
In this study EN-AC 43200 Aluminum alloy was subjected to secondary or interrupted aging following a T6 heat treatment. The 43200 alloy is a used widely in automotive industry for lowering weights of vehicles by substituting with ferrous alloys. This study covers the substitution of an automotive company’s part. 4320 Al alloy was melted under Argon atmosphere with an induction furnace, and cast into graphite molds. The samples were homogenized at 500 oC for 96 hours. Solutionizing treatment also done at 500 oC for 14 hours, following water quenching, T6 treatment was done at 250 oC for 2 hours ended with a water quench. Secondary aging trials were done at 100, 150 and 200 oC for 2, 4, 6 and 8 hours for each temperature range respectively. Tensile tests and microhardness tests were applied to for cast, T6 condition, and secondary aged samples. The samples were polished and observed for microstructure under optical microscope. Maximum strength value of 370 MPa, and hardness 113 Hv was...
Positive effect of natural pre-ageing on precipitation hardening in Al-0.44 at% Mg-0.38 at% Si alloy
Ultramicroscopy, 2009
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The artificial aging of Aluminum 2024, a critical aerospace alloy, represents a complex metallurgical process with significant implications for material performance. This study systematically investigates the precipitation hardening mechanisms through comprehensive thermal treatments at varying temperatures (178°C, 190°C, and 200°C) and durations, alongside natural aging. By analyzing hardness variations, microstructural transformations, and precipitate evolution, we reveal the intricate relationships between aging conditions and mechanical properties. Our research demonstrates that the precipitation sequence involving-Guinier-Preston zones, θ" and θ' phases, and and S phases evolution-plays a pivotal role in material strengthening. The 190°C treatment emerged as optimal, providing a stable hardening window with peak hardness maintained for up to 12 hours. Comparative analyses between artificial and natural aging processes highlight the superiority of controlled thermal treatments in accelerating precipitate formation and improving mechanical properties. The study provides an understanding of how temperature, time, and microstructural evolution interact to optimize the alloy's performance.
Microstructural characterization of interrupted aging on an AA7050 aluminum alloy
Materials Characterization, 2019
Interrupted aging heat treatments are used to maximize the gain in mechanical properties in 7xxx aluminum alloys through the production of a microstructure with a high density of fine precipitates, which are homogeneously dispersed in the aluminum matrix. In an interrupted aging heat treatment, the first stage, at higher temperature, aims at creating sites for subsequent nucleation of precipitate particles, while the second stage, at lower temperature, aims at the nucleation and growth of precipitate particles. The Interrupted aging heat treatment has been increasingly studied because it confers resistance levels similar to, or even higher than conventional heat treatments (e.g T6), in addition to producing a more stable microstructure. In this study, a microstructural characterization was carried out using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) in an AA7050 aluminum alloys that was submitted to aging heat treatments T7451, T6 and T6I4-65, seeking a better understanding of the microstructure produced in each heat treatment and the reasons of the gain in mechanical properties. The results indicated that the T6I4-65 interrupted aging heat treatment was the most efficient in creating sites for nucleation of phases in the aluminum matrix, when compared with other conditions, due to the higher density of particles of the phases η',η and T, in addition to being the only condition to have GPII zones and S phase in its microstructure.