Embrittlement of Al–Li–Cu–Mg alloys at slightly elevated temperatures: microstructural mechanisms of hardening

Starink, M.J.; Hobson, A; Sinclair, Ian; Gregson, P.J.

doi:10.1016/s0921-5093(00)00912-6

Cited by 31 publications

(17 citation statements)

References 38 publications

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“…It is further interesting to note that combination of data obtained by the present authors and coworkers [4,12,13,41,43,44] yields a detailed picture of how peaks A and B change in response to thermo-mechanical treatments. Compared to WQ samples, peak A is drastically reduced when 8090 is a) quenched at a slower rate (see also Ref.…”

Section: Identification Of Precipitatesmentioning

confidence: 53%

Microstrucure and strengthening of Al–Li–Cu–Mg alloys and MMCs: I. Analysis and Modelling of Microstructural changes

et al. 1999

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A complete and detailed analysis of the microstructural development during ageing in an 8090 (Al-2.3Li-1.2Cu-1Mg-0.1Zr) alloy, an 8090/20wt%SiC p MMC, an Al-1.5Li-Cu-Mg MMC and an Al-Cu-Mg MMC (all with similar Cu and Mg contents) has been performed. Volume fractions of all precipitates relevant for precipitation strengthening of the alloys (δ' phase, S' phase and GPB zones) have been determined using a recently derived method based on differential scanning calorimetry (DSC). The volume fractions have subsequently been successfully fitted using a novel model for transformation kinetics. The sizes of these precipitates have been analysed using newly derived expressions consistent with the latter model. As a result of dislocation generation around misfitting SiC particles the volume fractions of both GPB zones and S' phase depend strongly on the presence of these particles. Also the amount of Li present in the alloys influences the volume fractions of the phases significantly. The sizes of S' are similar for the four alloys. Introduction AimsMonolithic Al-based alloys for structural applications are generally strengthened by 4 basic mechanisms: precipitation strengthening, solution strengthening, grain and subgrain strengthening and strengthening by dislocations. The first two mechanisms depend strongly on composition of the alloy and on heat treatment and are generally employed in a metastable state, whilst the latter two mechanisms depend mostly on thermo-mechanical processing routes. In metal matrix composites (MMCs) additionally load transfer to ceramic inclusions in the matrix can increase the strength of the alloy (see e.g. [1,2]). Apart from this direct effect the presence of ceramic inclusions will also influence the precipitation in the matrix [1,3,4] and thus influence strengthening in an indirect way. The main aim of the present work and the companion paper [5] is to derive and validate a complete microstructure-property model for reinforced and unreinforced Al-Li-Cu-Mg type alloys and link this model with a novel model for the kinetics of microstructure development.

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Section: Identification Of Precipitatesmentioning

confidence: 53%

Microstrucure and strengthening of Al–Li–Cu–Mg alloys and MMCs: I. Analysis and Modelling of Microstructural changes

et al. 1999

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“…For example, in the Licontaining aluminum alloy 2090, secondary aging of peak-aged material has been found to reduce ductility and fracture toughness, and this has been ascribed to secondary precipitation of a fine dispersion of the Al 3 Li (d9) hardening phase throughout the matrix. [8] Secondary precipitation was also found to reduce the positive creep performance in the underaged condition of an experimental Al-Cu-Mg-Ag alloy. [9] Because secondary precipitation in aluminum alloys occurred generally in an uncontrolled manner, and in such cases had mostly an adverse effect on the mechanical properties, this phenomenon was initially considered to be problematic and undesirable.…”

Section: Introductionmentioning

confidence: 92%

Microstructural development and mechanical properties of interrupted aged Al-Mg-Si-Cu alloy

Buha

Lumley

Crosky

2006

Metall Mater Trans A

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The effects of a recently developed interrupted aging procedure on the microstructural development and mechanical properties of the commercial Al-Mg-Si-Cu alloy 6061 have been studied using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and mechanical testing. This so-called T6I6 temper involves partially aging the alloy at a typical T6 temperature (the underaging stage), quenching, then holding at a reduced temperature (in this case 65°C) to facilitate further hardening (the secondary aging stage), prior to final aging to peak properties at, or close to, the initial aging (T6) temperature (the reaging stage). The T6I6 aging treatment produces simultaneous increases in tensile properties, hardness, and toughness, as compared with conventional T6. The overall improvement in the mechanical properties of 6061 T6I6 is associated with the formation of a greater number of finer, and more densely dispersed, b0 precipitates in the final microstructure. Secondary precipitation took place during the interrupted aging stage of the T6I6 temper, resulting in the formation of a large number of Guinier-Preston (GP) zones that served as precursors to the needlelike b0 precipitates when elevated temperature aging was resumed.

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“…%) [19,20,21]. These 3 rd generation Al-Li alloys are now implemented on aircraft for lower wing skin, stringers, and fuselage skin as the disadvantages encountered on the first generations (reduced ductility, reduced fracture toughness and reduced thermal stability [22]) have been solved by an improvement of the chemical composition of the alloys and optimised thermo-mechanical treatments [19]. One of the alloys studied here is a low Li containing Al-Cu-Mg alloy, with composition close to those 3 rd generation AlLi alloys.…”

Section: Introductionmentioning

confidence: 99%

Al–Mg–Cu based alloys and pure Al processed by high pressure torsion: The influence of alloying additions on strengthening

Zhang

Gao

Starink

2010

Materials Science and Engineering: A

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The influence of alloying additions on strengthening of high pressure torsion (HPT) processed alloys was investigated using commercially pure Al (Al-1050 alloy) and five Al-(1-3)Mg-(0-4)Cu alloys (in wt%). Microhardness was measured on cross sections. For Al-1050 the microhardness reaches a peak at an effective strain of about 3 and subsequently decreases. The microhardness of Al-Mg-Cu alloys increases strongly and continuously with increasing equivalent strain. This workhardening rate is enhanced by increasing Mg content over the entire range of strain. Furthermore, the workhardening rates were higher in Cu-free and low Cu-containing (≤ 0.4%) Al-Mg alloys as compared to high Cucontaining Al-Mg alloy at strains less than 3. The results indicate that dislocation-solute and dislocation-cluster interactions play an important role in strengthening.

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Embrittlement of Al–Li–Cu–Mg alloys at slightly elevated temperatures: microstructural mechanisms of hardening

Cited by 31 publications

References 38 publications

Microstrucure and strengthening of Al–Li–Cu–Mg alloys and MMCs: I. Analysis and Modelling of Microstructural changes

Microstrucure and strengthening of Al–Li–Cu–Mg alloys and MMCs: I. Analysis and Modelling of Microstructural changes

Microstructural development and mechanical properties of interrupted aged Al-Mg-Si-Cu alloy

Al–Mg–Cu based alloys and pure Al processed by high pressure torsion: The influence of alloying additions on strengthening

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