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Shock-wave Synthesis of Titanium Diboride in Copper Matrix and Compaction of -Cu Nanocomposites
Lomovsky O.I.,Mali V.I.,Dudina D.V.,Korchagin M.A.,Kwon D.H.,Kim J.S.,Kwon Y.S. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
We studied formation of nanostructured -Cu composites under shock wave conditions. We investigated the influence of preliminary mechanical activation (MA) of Ti-B-Cu powder mixtures on the peculiarities of the reaction between Ti and B under shock wave. In the MA-ed mixture the reaction proceeded completely while in the non-activated mixture the reagents remained along with the product . titanium diboride. The size of titanium diboride particles in the central part of the compact was 100-300 nm.
Dina V. Dudina,Vyacheslav I. Mali,Alexander G. Anisimov,Natalia V. Bulina,Michail A. Korchagin,Oleg I. Lomovsky,Ivan A. Bataev,Vladimir A. Bataev 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.6
We present several possible microstructure development scenarios in Ti3SiC2-Cu composites during mechanical milling and Spark Plasma Sintering (SPS). We have studied the effect of in situ consolidation during milling of Ti3SiC2 and Cu powders and melting of the Cu matrix during the SPS on the hardness and electrical conductivity of the sintered materials. Under low-energy milling, (3-5) vol.%Ti3SiC2-Cu composite particles of platelet morphology formed, which could be easily SPS-ed to 92-95% relative density. Under high-energy milling, millimeter-scale (3-5) vol.%Ti3SiC2-Cu granules formed as a result of in situ consolidation and presented a challenge to be sintered into a bulk fully dense sample; the corresponding SPS-ed compacts demonstrated a finer-grained Cu matrix and more significant levels of hardening compared to composites of the same composition processed by low-energy milling. The 3 vol.% Ti3SiC2-Cu in situ consolidated and Spark Plasma Sintered granules showed an extremely high hardness of 227 HV. High electrical conductivity of the Ti3SiC2-Cu composites sintered from the granules was an indication of efficient sintering of the granules to each other. Partial melting of the Cu matrix, if induced during the SPS, compromised the phase stability and uniformity of the microstructure of the Ti3SiC2-Cu composites and thus it is not to be suggested as a pathway to enhanced densification in this system.
TiB<sub>2</sub>-Cu Interpenetrating Phase Composites Produced by Spark-plasma Sintering
Kwon, Young-Soon,V. Dudina, Dina,I. Lomovsky, Oleg,A. Korchagin, Michail,Kim, Ji-Soon The Korean Powder Metallurgy Institute 2003 한국분말재료학회지 (KPMI) Vol.10 No.3
Interpenetrating phase composites of $TiB_2$-Cu system were produced via Spark-Plasma Sintering (SPS) oi nanocomposite powders. Under simultaneous action of pressure, temperature and electric current titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a fine-grained skeleton. Increasing SPS-temperature and he]ding time promote densification due to local melting of copper matrix When copper melting is avoided the compacts contain 17-20% porosity but titanium diboride skeleton is still formed representing the feature of SPS . High degree of densification and formation of titanium diboride network result in increased hardness of high-temperature SPS-compacts.
Phase Analysis of the Mechanically Alloyed Fe-Si Powder by Differential Dissolution Technique
Kwon, Young-Soon,Kim, Hwan-Tae,Golubkova G.V.,Vlasov A.A.,Lomovsky O.I. 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.5
The binary Fe-Si elemental powders mixture (1:2 in atomic proportion) has been milled for different milling times in an attrition mill. The phase characterization of mechanically alloyed powder was investigated using the chemical method of differential dissolution (DD) and the X-ray diffraction (XRD) method. In powder specimens milled for more than 15 hr, ε-FeSi and unreacted Si were observed. The formation of a supersaturated solid solution of Si in ε-FeSi induced by mechanical alloying (MA) was also verified. The lattice parameter of the ε-FeSi of as-milled powders changed from 4.4876 Å to 4.4668 Å according to the increase of MA time. Based on the results of the DD analysis, unreacted Si could be classified as (1) crystalline Si, (2) Si supersaturated in ε-FeSi, or (3) amorphous Si. Therefore formation of the β-FeSi₂ after annealing could be explained by the reaction between the ε-FeSi and the Si classified into types (1) and (2). It seemed that the amorphous Si induced by MA did not react with the ε-FeSi during annealing at 700℃.
In-situ Synthesis of Cu-TiB<sub>2</sub> Nanocomposite by MA/SPS
Kwon, Young-Soon,Kim, Ji-Soon,Kim, Hwan-Tae,Moon, Jin-Soo,D.V Dudina,O.I. Lomovsky The Korean Powder Metallurgy Institute 2003 한국분말재료학회지 (KPMI) Vol.10 No.6
Nano-sized $TiB_2$ was in situ synthesized in copper matrix through self-propagating high temperature synthesis (SHS) with high-energy ball milled Ti-B-Cu elemental mixtures as powder precursors. The size of $TiB_2$ particles in the product of SHS reaction decreases with time of preliminary mechanical treatment ranging from 1 in untreated mixture to 0.1 in mixtures milled for 3 min. Subsequent mechanical treatment of the product of SHS reaction allowed the $TiB_2$ particles to be reduced down to 30-50 nm. Microstructural change of $TiB_2$-Cu nanocomposite during spark plasma sintering (SPS) was also investigated. Under simultaneous action of pressure, temperature and electric current, titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a interpenetrating phase composite with a fine-grained skeleton.