Browsing by Author "Koga, Guilherme Yuuki"
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Item Open Access The benefit of the glassy state of reinforcing particles for the densification of aluminum matrix composites(MDPI, 2022-05-07) Kvashnin, Vyacheslav I.; Dudina, Dina V.; Ukhina, Arina V.; Koga, Guilherme Yuuki; Georgarakis, KonstantinosIn metallic glass-reinforced metal matrix composites, the glassy phase can serve a dual purpose: (i) it can behave as soft binder and porosity remover during consolidation; and (ii) it can act as the hard reinforcing phase after densification. The present work aimed to demonstrate the benefit of the glassy reinforcing particles for the densification of aluminum matrix composites. The consolidation behavior of Al–50 vol.% Fe-based alloy mixtures prepared using a glassy Fe66Cr10Nb5B19 alloy powder (Tg = 521 °C, Tx = 573 °C) or a crystalline Fe62Cr10Nb12B16 alloy powder was studied under spark plasma sintering (SPS) and hot pressing (HP) conditions. The powders were consolidated by heating above the glass transition temperature of the glassy alloy (up to 540 °C in SPS and 570 °C in HP). When the coarse aluminum powder was used, the reinforcing particles formed chains within the microstructure. In composites formed from the fine Al powder, the particles of the Fe-based alloy were separated from each other by the metallic matrix, and the tendency to form agglomerates was reduced. The glassy state of the alloy was shown to be beneficial for densification, as the metallic glass acted as a soft binder. The densification enhancement effect was more pronounced in the case of reinforcing particles forming chains. The hardness of the Al–50 vol.% glassy Fe66Cr10Nb5B19 composites obtained by SPS was twice the hardness of the unreinforced sintered aluminum (110 HV1 versus 45 HV1).Item Open Access Interaction between Fe66Cr10Nb5B19 metallic glass and aluminum during spark plasma sintering(Elsevier, 2020-08-28) Dudina, Dina V.; Bokhonov, Boris B.; Batraev, Igor S.; Amirastanov, Yusif N.; Ukhina, Arina V.; Kuchumova, Ivanna D.; Legan, Mikhail A.; Novoselov, Aleksey N.; Gerasimov, Konstantin B.; Bataev, Ivan A.; Georgarakis, Konstantinos; Koga, Guilherme Yuuki; Guo, Yaofeng; Botta, Walter José; Jorge, Alberto MoreiraIn the area of metal matrix composites, novel reinforcing options are currently being evaluated. Particles of amorphous alloys present an interesting possibility to reinforce soft metals. In the present work, the interaction between Fe66Cr10Nb5B19 metallic glass and aluminum during spark plasma sintering (SPS) was studied for the first time. In order to trace the phase and microstructural changes upon sintering, mixtures containing 20 vol% and 50 vol% of metallic glass were subjected to SPS at 500–570 °C. After SPS at 500 °C, no reaction layer between the metallic glass particles and aluminum was observed. After SPS at 570 °C, a reaction layer containing Fe2Al5 and FeAl3 formed around the Fe-based cores. The Vickers hardness of composites obtained from mixtures containing 20 vol% Fe66Cr10Nb5B19 at 540 °C was 75 HV and increased to 280 HV after sintering at 570 °C due to the formation of thicker reaction layers at the interface. The hardness of the composite sintered from the mixture containing 20 vol% Fe66Cr10Nb5B19 at 570 °C was between the values predicted by Reuss and Voigt models. Comparison of results of SPS of the powder mixtures with those of SPS of a pre-compacted pellet and electric current-free annealing suggests that local heating at the interface caused by interfacial resistance may be an important factor influencing the reaction advancement at the interface and the formation of Al-containing intermetallicsItem Open Access Microstructure and mechanical properties of composites obtained by spark plasma sintering of Al–Fe66Cr10Nb5B19 metallic glass powder mixtures(MDPI, 2021-09-15) Dudina, Dina V.; Bokhonov, Boris B.; Batraev, Igor S.; Kvashnin, Vyacheslav I.; Legan, Mikhail A.; Novoselov, Aleksey N.; Anisimov, Alexander G.; Esikov, Maksim A.; Ukhina, Arina V.; Matvienko, Alexander A.; Georgarakis, Konstantinos; Koga, Guilherme Yuuki; Jorge, Alberto MoreiraAt present, metallic glasses are evaluated as alternative reinforcements for aluminum matrix composites. These composites are produced by powder metallurgy via consolidation of metallic glass-aluminum powder mixtures. In most studies, the goal has been to preserve the glassy state of the reinforcement during consolidation. However, it is also of interest to track the structure evolution of these composites when partial interaction between the matrix and the metallic glass is allowed during sintering of the mixtures. The present work was aimed to study the microstructure and mechanical properties of composites obtained by spark plasma sintering (SPS) of Al-20 vol.% Fe66Cr10Nb5B19 metallic glass mixtures and compare the materials, in which no significant interaction between the matrix and the Fe-based alloy occurred, with those featuring reaction product layers of different thicknesses. Composite materials were consolidated by SPS at 540 and 570 °C. The microstructure and mechanical properties of composites obtained by SPS and SPS followed by forging, composites with layers of interfacial reaction products of different thicknesses, and metallic glass-free sintered aluminum were comparatively analyzed to conclude on the influence of the microstructural features of the composites on their strength.Item Open Access Reactivity of a glassy and a crystalline Fe66Cr10Nb5B19 alloy towards aluminum during sintering: a comparative study(Elsevier, 2023-05-26) Kvashnin, Vyacheslav I.; Dudina, Dina V.; Bokhonov, Boris B.; Petrov, Sergey A.; Ukhina, Arina V.; Georgarakis, Konstantinos; Coury, Francisco Gil; Koga, Guilherme YuukiA glassy Fe66Cr10Nb5B19 alloy and its crystalline counterpart consisting of the α-(Fe,Cr), FeNbB and Fe2B phases were spark plasma sintered with aluminum at 570 °C to investigate the interfacial reactions in the systems. In the mixture containing the crystalline alloy, α-(Fe,Cr) and Fe2B reacted with aluminum forming the Fe-Al intermetallic reaction products. The crystallites of FeNbB were distributed in the intermetallic matrix. The absence of α-(Fe,Cr) and Fe2B in the composite sintered from the glassy alloy was confirmed by Mössbauer spectroscopy. Overall, under the short SPS processing, the crystalline alloy was found to be more reactive towards aluminum than the glassy alloy. An increased reactivity was due to the presence of α-(Fe,Cr), a Fe-rich phase, in the crystalline alloy.