• Title/Summary/Keyword: B4C grain

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Effect of Addition of Other Componene (B4C, Mn, TiB2, B) on TiC-Ni3Al Cermet (TiC-Ni3Al Cermet에 타성분(B4C, Mn, TiB2, B) 첨가의 영향)

  • 김지헌;이완재
    • Journal of Powder Materials
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    • v.9 no.5
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    • pp.352-358
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    • 2002
  • The effects of boron or manganese added as $B_4C$, Mn, $TiB_2$, B on TiC-30vo1.%$Ni_3Al$ cermet sintered at 1380 and $1400^{\circ}C$ for 1 hour, were examined in relation with shrinkage, relative density, microstructure, lattice parameter, hardness and fracture toughness ($K_{IC}$). The results are summarized as follows: 1) The highest shrink-age showed about 30.5% in the specimen added B$_4$C and the maximum relative density was about 99% in the specimen added $TiB_2$; 2) The grains of TiC were grown during sintering and made the surrounding structure by adding boron and manganese. The largest grain size showed about $2.8\mutextrm{m}$ in the specimen with boron sintered at $1400^{\circ}C$;3) The lattice parameter of TiC was about $4.325\AA$ and $Ni_3Al$ about $3.592\AA$ by adding other elements; 4) The highest hardness was about $1100kgf/\textrm{mm}^2$ in the specimen with B4C; 5) The fracture toughness ($K_{IC}$) showed about $15MNm^{-3/2}$ in the specimen added $TiB_2$.

On the microstructure of pressureless sintered $TiC-TiB_2$ composite refractory (상압소성된 $TiC-TiB_2$ 복합내화재의 미세구조)

  • 심광보;김현기;오근호
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.7 no.4
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    • pp.632-639
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    • 1997
  • Relative density and microstructure of the pressureless sintered TiC-$TiB_2$ composite has been studied. The maximum sintered density was 95% and the critical amounts of sintering aids were 1 wt% Fe and 3 wt% Ni. It was found that TiC matrix phase inhibited effectively grain growth of the dispersed $TiB_2$ phase. The TEM investigation reveals that the Ni-rich precipitates were solidified from the liquid phase, confirmed by the presence of the waved and/or step phase boundaries. The precipitates also acts as the origin of the dislocation formation in the matrix phases.

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Effect of MgB6 Addition on Synthesis of Hexagonal Boron Nitride (Hexagonal Boron Nitride의 합성에 있어서 MgB6 첨가의 효과)

  • Lee, Dae-Jin;Jee, Mi-Jung;Choi, Byung-Hyun;Lee, Mi-Jai;Cho, Nam-Hee;Cha, Mi-Sun
    • Journal of the Korean Ceramic Society
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    • v.46 no.1
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    • pp.53-57
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    • 2009
  • The h-BN powder was synthesized by amorphous $B_2O_3$ and activated carbon at $1550^{\circ}C$ in nitrogen atmosphere, whose properties were examined according to $MgB_6$ addition. Amount of $MgB_6$ addition was varied in the range of $0{\sim}$10\;wt% of the initial mixture. It was observed that $MgB_6$ addition led to an increase in the amount and the grain size of h-BN and decrease in the amount of $B_4C$ forming. When $MgB_6$ added 5 wt%, the amount and crystallinity of h-BN increased as the holding time at the synthesis temperature was prolonged. It was also confirmed that the regularity of three-dimensional ordering of h-BN increases.

A Study on the Densifcation of Stellite Fine Powder for Iniection Molding (사출성형용 Stellite미분말의 소결 치밀화에 관한 연구)

  • 임태환
    • Journal of Powder Materials
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    • v.4 no.2
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    • pp.113-121
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    • 1997
  • The densification of the compacts of Co+32%Cr+20%W+l.5%C, Co+32%Cr+20%W+3.0%C and Co+32%Cr+20%W+4.5%C sintered under $H_2$ gas or vacuum was investigated. The effect of V and B addition on the densification was also investigated. The densification of these compacts were always incomplete regardless of sintering atmosphere, temperature and time. The amounts of oxygen and carbon in compacts sintered in $H_2$ for 3.6ks at 1523K were 0.105~0.160 mass% and 0.33~0.89 mass%, respectively. And those in vacuum were 0.028~0.032% and 0.957~4.08%, respectively. Relative density(Ds) of Co+29%Cr+17%W+3.0%C compact containing 6%V and Co+32%Cr+20%W+2.97%C compact containing 0.03%B were 99 and 100%, respectively, indicating complete densification by solid phase sintering. Victors hardness of sintered compacts containing 6%V or 0.03%B were 632 and 568, showing 50~60% increase in comparison to those without V or B. These results can be explained in terms of oxidation/reduction of oxides and equilibrium pressure of CO in isolated pore, instead of presence of liquid formation and grain boundary separation from pores due to large grain growth.

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Effect of Crystallization Treatment on the Magnetic Properties of Amorphous Strips Based on Co-Fe-Ni-B-Si-Cr Containing Nitrogen

  • Cho H.J.;Kwon H.T.;Ryu H.H.;Sohn K.Y.;You B.S.;Park W.W.
    • Journal of Powder Materials
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    • v.13 no.4 s.57
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    • pp.285-289
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    • 2006
  • Co-Fe-Ni-B-Si-Cr based amorphous strips containing nitrogen were manufactured via melt spinning, and then devitrified by crystallization treatment at the various annealing temperatures of $300^{\circ}C{\sim}540^{\circ}C$ for up to 30 minutes in an inert gas $(N_2)$ atmosphere. The microstructures were examined by using XRD and TEM and the magnetic properties were measured by using VSM and B-H meter. Among the alloys, the amorphous ribbons of $Co_{72.6}Fe_{9.8}Ni_{5.5}B_{2.4}Si_{7.1}Cr_{2.6}$ containing 121 ppm of nitrogen showed relatively high saturation magnetization. The alloy ribbons crystallized at $540^{\circ}C$ showed that the grain size of $Co_{72.6}Fe_{9.8}Ni_{5.5}B_{2.4}Si_{7.1}Cr_{2.6}$ alloy containing 121 ppm of nitrogen was about f nm, which exhibited paramagnetic behavior. The formation of nano-grain structure was attributed to the finely dispersed Fe4N particles and the solid-solutionized nitrogen atoms in the matrix. Accordingly, it can be concluded that the nano-grain structure of 5nm in size could reduce the core loss within the normally applied magnetic field of 300A/m at 10kHz.

Effect of Heat Treatment on Joint Strength of 300Grade 18% Ni Maraging Steel Sheet Welded with Electron Beam (전자비임 용접된 300Grade 18% Ni 마르에이징강 박판의 이음강도에 미치는 열처리의 방향)

  • Jung, B.H.;Kim, H.G.;Kang, S.B.;Kim, W.Y.;Park, H.I.
    • Journal of the Korean Society for Heat Treatment
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    • v.6 no.4
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    • pp.185-193
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    • 1993
  • The effect and Condition of heat treatment on the tensile strength of welded joint was investigated in 300 grade 18% Ni-Co-Mo-Ti maraging steel sheets welded with electron beam. A good tensile strength of welded joint was obtained by following heat treatment cycle ; At $1100^{\circ}C$ the specimen was high temperature solution treated for 1 hour and then it was repeated solution treated at $900^{\circ}C$, $820^{\circ}C$ for 1 hour respectively to recrystallize the coarsened ${\gamma}$ grain. These heat treatment cycle was completed by an final aging heat treatment at $480^{\circ}C$ for 4 hour. Moreover, dissolution of dendrite, a significant decrease in seregation of Mo, Ti in weld metal were observed and also the coarsened ${\gamma}$ grain formed at $1100^{\circ}C$, $1200^{\circ}C$ changed to fine grain due to the effect of recrystallization.

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Low-Temperature Superplastic Deformation Behavior of Fine-Grained Ti-6Al-2Sn-4Zr-2Mo-0.1Si Alloy (미세 결정립 Ti-6Al-2Sn-4Zr-2Mo-0.1Si 합금의 저온 초소성 변형 거동)

  • Park, C.H.;Lee, B.;Lee, C.S.
    • Transactions of Materials Processing
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    • v.18 no.7
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    • pp.544-549
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    • 2009
  • This study aimed to elucidate the deformation mechanism during low-temperature superplasticity of fine-grained Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloy in the context of constitutive equation. For this purpose, initial coarse equiaxed microstructure was refined to $2.2{\mu}m$ via dynamic globularization. Globularized microstructure exhibited large superplastic elongations(434-826%) at temperatures of $650-750^{\circ}C$ and strain rate of $10^{-4}s^{-1}$. It was found that the main deformation mechanism of fine-grained material was grain boundary sliding accommodated by dislocation motion with both stress exponent (n) and grain size exponent (p) values of 2. When the alpha grain size, not sub-grain size, was considered to be an effective grain size, the apparent activation energy for low-temperature superplasticity of the present alloy(169kJ/mol) was closed to that of Ti-6Al-4V alloy(160kJ/mol).

Fabrication and Mechanical Properties of Porous Silicon Carbide Ceramics from Silicon and Carbon Mixture (실리콘과 카본을 이용한 다공질 탄화규소의 제조와 기계적 특성)

  • Kim, Jong-Chan;Lee, Eun Ju;Kim, Deug-Joong
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.429-433
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    • 2013
  • Silicon, carbon, and B4C powders were used as raw materials for the fabrication of porous SiC. ${\beta}$-SiC was synthesized at $1500^{\circ}C$ in an Ar atmosphere from a silicon and carbon mixture. The synthesized powders were pressed into disk shapes and then heated at $2100^{\circ}C$. ${\beta}$-SiC particles transformed to ${\alpha}$-SiC at over $1900^{\circ}C$, and rapid grain growth of ${\alpha}$-SiC subsequently occurred and a porous structure with elongated plate-type grains was formed. The mechanism of this rapid grain growth is thought to be an evaporation-condensation reaction. The mechanical properties of the fabricated porous SiC were investigated and discussed.

Microstructure and mechanical properties of B4C-SiC composites (탄화붕소-탄화규소 복합체의 미세구조와 기계적 특성)

  • So, Sung Min;Kim, Kyoung Hun;Park, Joo Seok;Kim, Min Suk;Kim, Hyung Sun
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.29 no.6
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    • pp.338-344
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    • 2019
  • B4C-SiC composites were fabricated using hot press sintering method without sintering additives at 1,900~2,000℃ under a pressure of 40 MPa. The crystal phase, relative density, microstructure, and mechanical properties of B4C-SiC composites were evaluated. When B4C and SiC were uniformly dispersed in the composite, grain growth was inhibited, and a sintered body with a fine and uniform microstructure, with improved mechanical properties, was fabricated. The relative density of B4C-SiC composites sintered under 2,000℃ of temperature and 40 MPa of pressure was over 99.8 %, and the bending strength and Vicker's hardness at 50 wt% of B4C were 645 MPa and 30.6 GPa, respectively.

Reactive Sintering of SiC (탄화규소의 활성화소결)

  • 김영욱;이준근
    • Journal of the Korean Ceramic Society
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    • v.20 no.2
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    • pp.115-122
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    • 1983
  • There has been many controversies about the effects of additive in sintering of SiC But no prior systematic work has been reported about the difference between the effects of B and $B_4C$ as additive. The sintering behavior of SiC and its strength are studied and the optimum concentrations of additives and sintering conditions for SiC are determined. The effects of B and $B_4C$ have same effects on reactive sintering of SiC except the easiness of transport via vapor phase for uniform distribution in case of B. The strength of sintered SiC without exaggerated grain growth is limited by surface flaws and is nearly independent of temperature up to 140$0^{\circ}C$.

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