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Annealing Effects in Cast Commercial Aluminium Al–Mg–Zn–Cu(–Sc–Zr) Alloys
Martin Vlach,Jakub Čížek,Veronika Kodetová,Tomáš Kekule,František Lukáč,Miroslav Cieslar,Hana Kudrnová,Lucia Bajtošová,Michal Leibner,Petr Harcuba,Jaroslav Málek,Volkmar Neubert 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
Precipitation reactions of the cast Al–3.4 at%Mg–2.7 at%Zn–0.80 at%Cu–0.10 at%Fe–0.05 at%Si alloy with and withoutaddition of 0.14 at%Sc and 0.06 at%Zr were characterized by electrical resistometry, electron microscopy, X-ray diffraction,thermal analysis, microhardness testing, and positron annihilation. The AlMgZnCuScZr alloy contains a grain boundaryT-phase (Mg32(Al,Cu,Zn)49) with a cubic and/or quasicrystalline structure. The AlMgZnCu alloy contains a mixture ofMgZn2-and the T-phase. Primary multilayer Al3(Sc,Zr) particles precipitated during casting and subsequent cooling. Theparticles have a layered Al3(Sc,Zr) + α-Al + Al3(Sc,Zr) structure, i.e. consist of regions enriched with both Sc and Zr. Smallatomic Mg,Zn(,Cu)-rich clusters coherent with the matrix were formed during the cooling of both alloys and/or in the courseof their storage at ambient temperature. Their dissolution enables precipitation of the transient η′- and/or stable η-phasesof the AlZnMgCu system in both investigated alloys. The effective activation energy for the dissolution of the clusters wascalculated as ~ 103 kJ/mol. Annealing of the AlMgZnCuScZr alloy above 300 °C leads to a formation of the secondaryAl3(Sc,Zr) particles which cause precipitation hardening and guarantee thermal stability of mechanical properties. Additionof Sc and Zr micro alloying elements resulted in a substantial grain refinement. The grain size remains unchanged upto isochronal annealing at 390 °C.
Ultrasonic Treatment of Ti-5Al-0.5 V Alloy Subjected to Equal-Channel Angular Pressing
Aygul A. Mukhametgalina,Mariya A. Murzinova,Ayrat A. Nazarov,Asiya A. Samigullina,Miloš Janeček,Josef Stráský,Kristína Bartha,Jakub Čížek 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.5
Microstructure and room temperature mechanical properties of α-titanium alloy Ti-5Al-0.5 V subjected to equal channelangular pressing (ECAP) and subsequent ultrasonic treatment (UST) have been studied. The ECAP was carried out at 600 °Cby route Bcand the UST at the frequency of 20 kHz and amplitude of compression-tension stresses of 100 MPa for processingtime of 60 s. The dislocation densities after ECAP and subsequent UST were estimated by x-ray diffraction and positronlifetime spectroscopy. By the latter, vacancy concentration also was determined. It has been shown that UST results in avery little increase in the dislocation density and vacancy concentration and has no considerable effect on the mechanicalproperties of the ECAP-ed titanium alloys. Basing on the data obtained and earlier published results of computer simulationsof the behavior of nonequilibrium grain boundaries in Ni and Ti under the action of ultrasound it is concluded thatthe structural transformations in Ti under UST occur at much higher stresses than in Ni, in which UST results in significantmodifications of the structure and properties.