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- 저자 : Harcuba, P. (검색결과 2 건)
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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.
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Strength enhancement of high entropy alloy HfNbTaTiZr by severe plastic deformation
Č,í,ž,ek, J.,Hauš,ild, P.,Cieslar, M.,Melikhova, O.,Vlasá,k, T.,Janeč,ek, M.,Krá,l, R.,Harcuba, P.,Luká,č,, F.,Zý,ka, J.,Má,lek, J.,Moon, J Elsevier 2018 Journal of alloys and compounds Vol.768 No.-
<P><B>Abstract</B></P> <P>Refractory metal high entropy alloy HfNbTaTiZr with ultrafine grained structure and grain size of ≈80 nm was processed by high pressure torsion. The development of microstructure, lattice defects and mechanical properties with increasing strain was examined. Grain refinement of HfNbTaTiZr alloy deformed up to the equivalent strain <I>e</I> ≈ 50 resulted in a significant enhancement of strength while keeping sufficient ductility. However, further straining <I>e</I> > 100 led to a decrease of strength and the loss of ductility due to the decomposition of solid solution facilitated by vacancies introduced by severe plastic deformation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High entropy alloy HfNbTaTiZr was nanostructured by high pressure torsion. </LI> <LI> Grain size of 80 nm was achieved by deformation to the equivalent strain e = 5. </LI> <LI> Structure refinement resulted in remarkable enhancement of strength of the alloy. </LI> <LI> Ductility remains sufficient for good workability. </LI> <LI> Further deformation to very high strains resulted in loss of strength. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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