The effect of silver on microstructural evolution in two 2xxx series Al-alloys with a high Cu:Mg ratio during ageing to a T8 temper

Abstract

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Effect of pre-straining on the aging behavior and mechanical properties of an Al–Cu–Mg–Ag alloy

“…This phase is a coherent modification of the equilibrium θ-phase (Al 2 Cu) that forms as a uniform dispersion of thin, hexagonal plates with large aspect ratios (diameter/thickness) on the {111} α habit planes [2][3][4][5][11][12][13][14][15]. The replacement of the Al atoms in the entire first and second layers on the broad faces of the Ω-phase plate in the direction normal to the Ω/Al interface with either Ag or Mg, respectively, lowers the interfacial energy of the (001) Ω //(111) α interface and aids in accommodation of the misfit and the volumetric strain that exist between the Ω-phase and the Al lattice [4,5].…”

“…In other words, these alloys are subjected to a T8 temper [9,10,14]. In the T8 process, the cold working resulted in a high density of dislocations and dramatically increased the number density of the θ 0 -phase, which forms rectangular or octagonal plates parallel and semicoherent to the {100} α planes on lattice dislocations at the expense of the Ω-phase [15][16][17].…”

“…In the T8 process, the cold working resulted in a high density of dislocations and dramatically increased the number density of the θ 0 -phase, which forms rectangular or octagonal plates parallel and semicoherent to the {100} α planes on lattice dislocations at the expense of the Ω-phase [15][16][17]. Concurrently, the passage of dislocations through the matrix during deformation prior to aging disrupts the clustering of Ag and Mg atoms and also alters the vacancy content [14,15,18]. As a result, the precipitation sequence in a pre-deformed structure can be re-written as [15] SSSS-Ω À phase þ θ 0 À phase-θ À phase þ S À phase ð2Þ…”

Effect of Annealing on Structure and Mechanical Behavior of an AA2139 Alloy

“…These alloys exhibit excellent mechanical properties including high strength, superior creep resistance and fracture toughness, fatigue life due to the formation of the fine and uniform dispersion of the -phase with plate-like shape on the {111} α planes of the aluminum matrix [1,2]. Numerous works were dealt with examination of the precipitation behavior and mechanical properties of these alloys [2][3][4][5]. However, the effect of precipitates produced by over-aging on workability of these alloys was considered in very limited number of studies [6] despite its importance for cold rolling and forging, where metal can be shaped through plastic deformation without introducing any defect.…”

Influence of welding parameters and post-weld aging on tensile properties and fracture location of AA2139-T351 friction-stir-welded joints

“…Mg is known to be crucial for the formation of the W phase in Al-Cu alloys, and Ag accelerates its precipitation. Indeed, the strong interaction between Ag and Mg results in the generation of Mg-Ag clusters which act as sites for the nucleation of W. Moreover, W is more stable than q' at the usual aging temperatures (≤ 200 °C), indicating that the 2139 exhibits excellent mechanical strength up to 200 °C 19,20 . In T351 condition, the 2139 is hardened by the Cu GP-zone formation, as demonstrated 21 .…”