Precipitate assemblies formed on dislocation loops in aluminium-silver alloys

Rosalie, Julian M.; Bourgeois, Laure; Muddle, Barrington Charles

doi:10.1080/14786430902932862

Cited by 6 publications

(8 citation statements)

References 18 publications

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“…The Al-Ag (Figure 1(a)) and Al-Ag-Cu (Figure 1(b)) alloys aged for ≤0.5 h at 200 o C contained Ag-rich Guinier-Preston (GP) zones and a sparse distribution of γ ′ precipitates. The precipitates formed structured assemblies in association with dislocation loops that have been described previously [21,22] and are not discussed in detail here.…”

Section: Resultsmentioning

confidence: 79%

“…This layering extends over a thickness of seven close-packed planes, equivalent to three times the unit cell height and the matrix planes are commensurate across the precipitate. Such commensurate precipitates were invariably found as isolated, single precipitates, rather than as members of the structured precipitate assemblies described in [21,22].…”

Section: Stemmentioning

confidence: 99%

“…Precipitation has been observed on Frank dislocation loops [19,6] and dislocations which provide a faulted surface [6,19,20]. When the γ ′ phase formed on dislocation loops, precipitation occurred only on the faulted surfaces [21,22]. In addition, silver-rich GP zones that form in advance of the γ ′ phase persist in the microstructure despite prolonged ageing [6], indicating poor nucleation behaviour.…”

Section: Introductionmentioning

confidence: 99%

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Nucleation and growth of the γ′(AlAg2) precipitate in Al–Ag(–Cu) alloys

2011

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Precipitation of the γ ′ (AlAg 2 ) phase was investigated in Al-Ag(-Cu) alloys using high resolution transmission electron microscopy and scanning transmission electron microscopy. Precipitation commenced with segregation of silver to stacking faults, followed by thickening in steps corresponding to single unit cell ledges. In conjunction with gradual segregation of silver and aluminium into ordered layers this yielded γ ′ phase platelets with a thickness of either 2 or 3× the AlAg 2 c-lattice parameter Plates with a thickness of 2c(AlAg 2 ) would not achieve self-accommodation of the shape strain for transformation. Further thickening of the precipitates was slow, despite considerable silver segregation around the precipitates. Growth by the addition of single unit cell height ledges is expected to lead to an additional shear strain energy barrier to ledge nucleation and this may contribute to a process of nucleation-limited, growth.

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Section: Resultsmentioning

confidence: 79%

Section: Stemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nucleation and growth of the γ′(AlAg2) precipitate in Al–Ag(–Cu) alloys

2011

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“…The Vickers hardness curves measured for the ternary Al 98.2 Ag 0.9 Cu 0.9 alloy are presented in Figure 1, along with those for Al-Ag [28] and Al-Cu [24] binary alloys. The copper containing alloys experienced a more significant increase in hardness than those with equal atomic amounts of silver.…”

Section: Hardness Measurementsmentioning

confidence: 99%

Precipitate assemblies formed on dislocation loops in aluminium-silver-copper alloys

Rosalie

Bourgeois

Muddle

2009

Philosophical Magazine

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The precipitation microstructure of the γ ′ (AlAg 2 ) intermetallic phase has been examined in aluminium-silver-copper alloys. The microstructure developed in an Al-0.90at.%Ag-0.90at.%Cu alloy was significantly different from that reported for binary Al-Ag alloys. The orientation relationship between the matrix and precipitate was unchanged; however, the γ ′ phase formed as aggregates with a two-dimensional open assemblies. Each such assembly contained two variants of the γ ′ phase alternately arranged to form a faceted elliptical unit. The θ ′ (Al 2 Cu) phase formed on these assemblies after further ageing. The faceted elliptical assembly morphology has not been previously reported for the γ ′ precipitate. The change in precipitation behaviour was attributed to copper modifying the as-quenched defect structure of the matrix. This precipitation morphology clarifies earlier observations on the precipitate number density and mechanical properties of aluminium-silver-copper alloys.

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“…The absence of Mg near interface for joint with silver interlayer results in less favourable condition for the formation of Fe 2 Al 5 , and the situation is more favorable for the silver/aluminium intermetallic formation at the interface. This intermetallic compound is reported to be significantly softer than that formed between iron and aluminium and hence much greater thickness can be tolerated in the attainment of good quality welds between aluminium and its alloy to low alloy steel [24].…”

Section: Discussionmentioning

confidence: 99%

Friction welding of AA6061 to AISI 4340 using silver interlayer

Reddy

2015

Defence Technology

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The present work pertains to the study on joining of AA6061 and AISI 4340 through continuous drive friction welding. The welds were evaluated by metallographic examination, X-ray diffraction, electron probe microanalysis, tensile test and microhardness. The study reveals that the presence of an intermetallic compound layer at the bonded interface exhibits poor tensile strength and elongation. Mg in AA6061 near to the interface is found to be favourable for the formation and growth of Fe 2 Al 5 intermetallics. Introduction of silver as an interlayer through electroplating on AISI 4340 resulted in accumulation of Si at weld interface, replacing Mg at AA6061 side, thereby reducing the width of intermetallic compound layer and correspondingly increasing the tensile strength. Presence of silver at the interface results in partial replacement of FeeAl based intermetallic compounds with AgeAl based compounds. The presence of these intermetallics was confirmed by X-ray diffraction technique. Since AgeAl phases are ductile in nature, tensile strength is not deteriorated and the silicon segregation at weld interface on AA6061 in the joints with silver interlayer acts as diffusion barrier for Fe and further avoids formation of FeeAl based intermetallics. A maximum tensile strength of 240 MPa along with 4.9% elongation was obtained for the silver interlayer dissimilar metal welds. The observed trends in tensile properties and hardness were explained in relation to the microstructure.

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Precipitate assemblies formed on dislocation loops in aluminium-silver alloys

Cited by 6 publications

References 18 publications

Nucleation and growth of the γ′(AlAg2) precipitate in Al–Ag(–Cu) alloys

Nucleation and growth of the γ′(AlAg2) precipitate in Al–Ag(–Cu) alloys

Precipitate assemblies formed on dislocation loops in aluminium-silver-copper alloys

Friction welding of AA6061 to AISI 4340 using silver interlayer

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