• Title/Summary/Keyword: whisker

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Mechanical Properties and Strengthening Mechanisms of Cordierite-SiC Whisker Ceramic Composites (코디어라이트-SiC 위스커 복합재료의 기계적 성질과 강화기구)

  • ;Weisskopf
    • Journal of the Korean Ceramic Society
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    • v.23 no.6
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    • pp.59-65
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    • 1986
  • Flexural strength fracture toughness and strengthening mechanisms of cordierite ceramics reinforced by SiC whiskers up to 40vol% were investigated. The specimens were hot pressed at Ar atmosphere. The porosity increased with the SiC whisker content. Flexural strength and single edge notch beam fracture toughness were measured up to 1,000$^{\circ}C$. Extrapolating to zero porosity the reinforced composites exhibited in-creasings in flexural strength and fracture toughness with the SiC whisker content. The composites were strengthened mainly by load transfer crack impediment and partially by crack deflection mechanisms. Impurities played an important role in determining the mechanical properties of the composites.

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A Study on the Fatigue Strength Evaluation of Metal Matrix Composite (금속기 복합재료의 피로강도 평가에 관한 연구)

  • 김윤해
    • Journal of Advanced Marine Engineering and Technology
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    • v.18 no.2
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    • pp.41-53
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    • 1994
  • In this paper, rotating-bending fatigue tests of the SiC-whisker- reinforced 6061-T6 aluminum alloy and 6061-T6 alumiunm alloy made by power metallurgy were carried out to investigate the fatigue characteristics of plain and notched specimens at room temperature. The fatigue mechnisms in both materials were clarified through successive surface observations using the plastic replica method. In the case of the SiC-whisker-reinforced composites, there are whisker rich and poor zones and the fatigue crack is nucleated from the end of whiskers near the boundary. On the other hand, in the case of the 6061-T6 aluminum alloy, the fatigue crack is nucleated from defects and propagates by shear. Moreover, the results were discussed based on linear notch mechanics.

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A study on the microstructure of cordierite glass-ceramics composites containing $Si_3{N_4}$ whisker ($Si_3{N_4}$휘스커 첨가량에 따른 코디에라이트 glass-ceramics 복합체의 미세구조)

  • 한병성;최효상
    • Electrical & Electronic Materials
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    • v.7 no.1
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    • pp.1-6
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    • 1994
  • Cordierite based glass ceramics has become an electronic substrate material for electronic circuits and the use of whickers for improving strength and toughness is evident. Pure cordierite containing 15 vol.% silicon nitride were sintered by hot-prossing and it has above 99% density. Especially, it is assumed that toughening increasing at the more high sintering temperature relevants to the glass phase increasing, as showned in the roughness of the fracture surfaces. It was directionally dependent of whisker drirection during processing.

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Degradation Behavior of Solder Joint and Implementation Technology for Lead-free Automotive Electronics (자동차 전장제품의 무연솔더 적용기술 및 솔더 접합부 열화거동)

  • Hong, Won Sik;Oh, Chul Min
    • Journal of Welding and Joining
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    • v.31 no.3
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    • pp.22-30
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    • 2013
  • Due to ELV banning, automotive electronics cannot use four kinds of heavy metal element (Pb, Hg, Cd, $Cr^{6+}$) from 2016. Therefore, this study was focused on degradation characteristics of Sn-3.0Ag-0.5Cu Lead-free solder joint with OSP and ENIG finsh under various reliability assessment method, as like to thermal shock test and high temeprature/high humidity test with test duration for cabin electronics. Also, we compared bonding strength degradation to other advanced research results of electronic control unit for engine room because of difference service temperature with mount location in automotive. Whisker growth phenomenon and mitigation method which were essentially consideration items for Pb-free car electronics were examined. Conformal coating is a strong candidate for mitigating whisker growth in automotive electronics. Necessary condition to adapt Pb-free in car electronics was shown.

Fabrication of AC4A/SiCw composite by squeeze casting (III) - Mechanical characteristics - (용탕단조법에 의한 AC4A/SiCw 복합재료 제조에 관한 연구(III) - 기계적 특성 -)

  • Moon, Kyung-Cheol;Lee, Jun-Hee;Yoon, Eui-Pak
    • Journal of the Korean Society for Heat Treatment
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    • v.7 no.3
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    • pp.160-168
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    • 1994
  • This was studied about mechanical characteristic of AC4A/SiCw 10-30% reinforced composites. Tensile strength of pressed base metal(base metal) with SiCw preform was higher than without pressed base metal(AC4A). If SiCw whisker volume fraction was increased, tensile strength at room temperature was increased. And tensile strength of SiCw 30% was about $35kg/mm^2$. Tensile strength of SiCw 30 % $400^{\circ}C$ at same time aging was the most excellence, about $40kg/mm^2$. The fracture energy value of composite material at three point bending test was higher than AC4A. Dislocation at matrix of composite material was evenly distributed. But dislocation around whisker of composite material was more existed than matrix. The reasom was thought of pile-up around whisker.

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Microstructure and Mechanical Strength of Hardened Paste of Hydroxyapatite Cement Containing Whisker Phase (휘스커상을 함유한 수산화아파타이트시멘트 경화체의 미구조-강도 특성)

  • 손영도;송태웅
    • Journal of the Korean Ceramic Society
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    • v.36 no.12
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    • pp.1342-1349
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    • 1999
  • In order to improve the density and the mechanical strength without change in chemical composition the hardened pastes of hydroxyapatite cement were reinforced with powders and/or whiskers of hydroxyapatite. The powders behaved as a seed of hydroxyapatite formation rather than a filler while the whiskers were mrerly dispersed in matrix and capillary pores of the hardened bodies leading to increase in mechanical strength. But the increase in strength But the increase in strength was nnt enough owing to the lack of homogeneous dispersion of the fibers. The highest diametral tensile strength of 18.5 MPa was measured at the hardened hydroxyapatite body in which well-dispersed whisker phase formed uniformly during hydro-thermal curing of power-added and dry-formed hydroxyapatite cement.

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Thermal Characteristics of SiC Whisker Reinforced $Al_2$O$_3$-SiC Composite (SiC 휘스커 보강 $Al_2$O$_3$-SiC 복합체의 열간특성)

  • 김윤주;나용한
    • Journal of the Korean Ceramic Society
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    • v.35 no.1
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    • pp.1-4
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    • 1998
  • SiC whisker reinforced Al2O3-SiC composite was fabricated by reaction synthesis method whish is cost ef-fective and allows good dispersion of whiskers. Fracture strength at room temperature showed the highest value with 150$0^{\circ}C$ reaction temperature because a lot of SiC whiskers was formed. Fracture strength at 135$0^{\circ}C$ did not show big differences with reaction temperature due to agglomeration of whiskers and formation of sil-icon oxynitride during hot MO(modulus of rupture) test probably promoting grain boundary sliding.

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Turning of Plastic Mold Steel(STAVAX) using Whisker Reinforced Ceramic (단침보강 세라믹 공구를 이용한 플라스틱 금형강(STAVAX)의 선삭가공)

  • Bae, Myung-Il;Lee, Yi-Seon
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.6
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    • pp.36-41
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    • 2012
  • In this study, we turning plastic mold steel (STAVAX) against cutting speed, depth of cut, feed rate using whisker reinforced ceramic tool (WA1). To predict cutting force, analyze principal, radial, feed force with multi-regression analysis. Results are follows: From the analysis of variance, affected factor to cutting force feed rate, depth of cut, cutting speed in order and cutting speed was very small affect to cutting force. From multi-regression analysis, we extracted regression equation and the coefficient of determination$(R^2)$ was 0.9, 0.88, 0.856 at principal, radial and feed force. It means regression equation is significant. From the experimental verification, it was confirmed that principal, radial and feed force was predictable by regression equation.

Effect of Silicon Nitride Whisker Content on the Flexural Strength of Silicon Nitride-Boron Nitride-Silicon Carbide Multi-Layer Composites

  • Park, Dong-Soo;Cho, Byung-Wook
    • Journal of the Korean Ceramic Society
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    • v.40 no.9
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    • pp.832-836
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    • 2003
  • Multi-layer ceramic composites were prepared by tape casting followed by hot pressing using silicon nitride layer with silicon nitride whiskers, silicon nitride layer with silicon carbide particles and boron nitride-alumina layer. The whiskers were aligned during the casting. As the whisker content of the silicon nitride layer was increased up to 10 wt%, the flexural strength of the multi-layer composite was increased. However, further increase of the whisker content in the layer resulted in a rapid decrease of the strength of the composite. The results suggest that the strength of multi-layer ceramic composite showing non-catastrophic failure behavior can be significantly improved by incorporating the aligned whiskers in the layers.

Preparation of AlN/SiC Whisker Composite by Reaction Sintering Process (반응소결법에 의한 AlN/SiC 휘스커 복합체의 제조)

  • 박정현;김용남;유재영;강민수
    • Journal of the Korean Ceramic Society
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    • v.36 no.2
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    • pp.193-202
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    • 1999
  • Al powder, AlN powder, SiC whisker and sintering aids were wet-mixed, and then the specimens prepared with mixed powder were reacted by nitridation at 600∼1400$^{\circ}C$ for 5 hrs. It was cleat that the higher nitridation and the more SiC whisker content were, the better bending strength was. The specimen of Al50/AlN50 reacted at 1400$^{\circ}C$ for 5hrs had the nitridation percent of 97%, the shrinkage under 2%, and the relative density of 78%. And the maximum bending strength of reaction-bonded specimen was 250 MPa. The specimens completely nitrided were post-sintered at 1700, 1800 and 1900$^{\circ}C$ for 2hrs. The post-sintered body had the shrinkage under 6% and the relative density of 86%. Because of the formation of solid solution between AlN and SiC whisker over 1800$^{\circ}C$, the promotion of mechanical properties according to SiC whisker addition was not observed. The post-sintered body had the maximum bending strength of 195 MPa.

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