Effect of Natural Aging on Mechanical Response of the Artificially Aged EN AW 6063 Aluminium Alloy

Abstract

The effect of natural pre-aging time (from 0.1 to 10000 h) on mechanical response during subsequent artificial aging of EN AW 6063 aluminium alloy at 170°C was investigated using Vickers microhardness measurements, tensile test analysis and transmission electron microscopy characterization. The microhardness and tensile strength of EN AW 6063 alloy increased slightly with natural aging time. Afterward, the artificial ageing from 18 to 20 hours induced the maximum increasing of hardness and strength for variously naturally pre-aged states of alloy. But, it was found that when pre-aging time was prolonged from 0.1 h to 10000 h, the mechanical response of artificial aging applied for the pre-aged alloy states was slightly improved. It was suggested, that as pre-aging time was increased, the size of β'-phase particles formed in solid solution of pre-aged alloy state during artificial aging was decreased and their amount was increased.

Study of thermal properties of the aluminium EN AW 2024-T3 alloy

“…The exothermic heat effect during the initial heating of the studied alloy indicates the precipitation process, which is characterized by the release of heat. In commercial EN AW 2024 alloy precipitation sequence includes the formation of Guinier-Preston-Bagaryatsky (GPB) zones followed by precipitation of S and S metastable phases before the precipitation of stable S-Al 2 CuMg phase [17,31]. According to the results of Zmywaczyk et al [6] and Semnani and Degischer [32], the exothermic heat effect in the temperature range identified in the present study is related to the precipitation of S and S phases.…”

“…Some other phases can be found depending on the alloy composition (primarily Cu content and Cu/Mg ratio) and thermal treatment parameters [17]. Starke and Staley [20] confirmed the existence of intermetallic particles of AlCuFe and AlFeMnSi phases in addition to the standard S and θ phases.…”

“…Therefore, it is kinetically more suitable to nucleate coherent metastable phases firstly, which have a lower nucleation barrier [2]. According to the literature, the precipitation of the main strengthening phases during aging goes through the following paths [17]: (i) from supersaturated solid solution Guinier-Preston--Bagaryatsky (GPB) zones firstly precipitate; then S metastable phase (fully coherent with the matrix) occurs; whereupon the S metastable phase (semicoherent with the matrix) precipitates; finally at the end of precipitation sequence S(Al 2 CuMg) equilibrium phase precipitates [18]; (ii) similarly, from supersaturated solid solution Guinier-Preston (GP) zones firstly precipitate, then θ metastable phase precipitates, after which the θ metastable phase occurs, finally at the end of precipitation sequence the θ(Al 2 Cu) equilibrium phase forms [19].…”

Residual stress and yield strength evolution with annealing treatments in an age-hardenable aluminum alloy matrix composite

“…Moreover, the diffusion length increases; this implies that the density of nuclei progressively decreases, and the distance between precipitates increases. This reduces the strengthening effect [52,53]. The precipitation kinetics is accelerated in MMCs in comparison to monolithic alloys: the presence of a larger dislocation density enhances diffusion phenomena.…”