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Optimizing the mechanical properties of Al-4.5Cu-xSi alloys through multi-pass friction stir processing and post-process aging

Mostafavi M., Taghiabadi R., Jafarzadegan M.

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e11, 2022

EN

The effect of post-process aging on the microstructure and mechanical properties of multi-pass friction stir processed (FSPed) Al-4.5Cu alloy containing Si (1, 3, and 5 wt.%) was studied. According to the results, adding Si improved the fluidity and decreased the porosity content of the alloy. The addition of Si up to 3 wt.% also enhanced the mechanical properties. However, further addition of Si up to 5 wt.% impaired the tensile properties. Applying the first pass of FSP improved the tensile strength and fracture strain of the alloy containing 3 wt.% Si by 25 and 125%, respectively. However, the second and fourth pass of FSP substantially improved the fracture strain, but deteriorated the hardness and tensile strength of the alloy containing 3 wt.% Si. Post-FSP aging at 180 °C for 8 h significantly improved the mechanical properties. For instance, compared to the as-cast condition, the hardness, tensile strength, fracture strain, and toughness of post-aged four-pass FSPed Al-4.5Cu-3Si alloy increased by 107, 108, 175, and 310%, respectively. According to the fractography results, the fracture surface morphology of Al-4.5Cu-3Si alloy changed from a quasi-cleavage mode in as-cast condition to a ductile-dimple fracture mode after post-FSP aging.

2

Refinement of Al-5%Cu and Al-25%Cu Alloys by Means of KoBo Methods

Rodak K., Brzezińska A., Sobota J.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1477--1482

EN

This study was undertaken to investigate the effect of severe plastic deformation (SPD) by extrusion combined with reversible torsion (KoBo) method on microstructure and mechanical properties of Al-5Cu and Al-25Cu alloys. The extrusion combined with reversible torsion was carried out using reduction coefficient of λ = 30 and λ = 98. In this work, the microstructure was characterized by light microscopy (LM), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Compression test and tensile test were performed for deformed alloys. The binary Al-5Cu and Al-25Cu alloys consist of the face cantered cubic (FCC) α phase in the form of dendrites and tetragonal (C16) θ-Al2Cu intermetallic phase observed in interdentritic regions. The increase of Cu content leads to increase of interdentritic regions. The microstructure of the alloys is refined after applying KoB deformation with λ = 30 and λ = 98. Ultimate Tensile Strength (UTS) of Al-5Cu alloy after KoBo deformation with λ = 30 and λ = 98 reached about 200 MPa. UTS for samples of Al-25Cu with λ = 30 and λ = 98 increased compared to Al-5Cu alloy and exceed 320 MPa and 270 MPa respectively. All samples showed increase of plasticity with increase of reduction coefficient. Independently of reduction coefficient, the compressive strain of Al-5Cu alloys is about 60%. The Al-25Cu alloy with λ = 98 showed the value of compressive strain exceed 60%, although for this same alloy but with λ = 30, the compressive strain is only 35%.

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Thermodynamics And Concentration Fluctuations Of Liquid Al-Cu And Al-Zn Alloys

Trybuła M., Jakse N., Gąsior W., Pasturel A.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

649--655

EN

Thermodynamic properties of liquid Al-Cu and Al-Zn alloys are investigated using the free volume model. We also analyse local atomic arrangements and concentration fluctuations in both liquid binary alloys from the determination of the Warren-Cowley short-range order. For liquid Al-Cu alloys, our findings indicate a strong preference for heteroatomic nearest-neighbors bonds on the Cu-rich side and weaker ones in the Al-rich part while for the liquid Al-Zn alloy, a tendency to the phase separation is observed. Basing on Darken’s thermodynamic relationship, diffusivity has been examined for both liquid alloys.

PL

W oparciu o model swobodnej objętości zostały zbadane właściwości termodynamiczne ciekłych stopów Al-Cu i Al-Zn oraz lokalne środowisko atomów w celu obliczenia parametru bliskiego zasięgu Warren-Cowleya. W ciekłych stopach Al-Cu zaobserwowano silną tendencję do tworzenia wiązań hetero-atomowych w obszarze bogatym w Cu, natomiast w obszarze stężeń bogatych w Al znacznie słabszą. W przypadku ciekłych stopów Al-Zn obliczenia wskazują na tendencję do segregacji atomów. Dyfuzja w dyskutowanych stopach została przeanalizowana w oparciu o termodynamiczną definicję podaną przez Darkena.