• Steel and Composite Structures
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• 제19권3호
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• pp.777-787
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• 2015

Production and properties of metal matrix composites reinforced with an in-situ high aspect ratio $AlB_2$ flake have been investigated. Boron 2.2wt.% was dissolved in pure Al and Al-Cu alloy at $1300^{\circ}C$ by adding directly boron oxide which resulted in 4 vol.% reinforcing phase. The in-situ $AlB_2$ flake concentration was increased up to 30 vol.% in order to increase the tensile strength of the composites. Hardness, compressive strength and tensile strength of the composite were measured and compared with their matrix. Results showed that 30 vol.% $AlB_2/Al$ composite show a 193% increase in the compressive strength and a 322% increase in compressive yield strength. Results also showed that ductility of composites decreases with adding $AlB_2$ reinforcements.

• Journal of Advanced Marine Engineering and Technology
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• 제27권1호
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• pp.124-133
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• 2003

Ti-25Al-xNb (x=0, 3, 7, 11, 13 at. %) alloys and 18 vol. % TiB/(Ti-25Al-11Nb) metal matrix composite were fabricated by spark plasma sintering process at 900-120$0^{\circ}C$. Microstructural characteristics of the sintered bodies were identified by SEM, EDX analysis, X-ray diffraction, and differential scanning calorimeterric method. $Ti_3Al$ alloy was consisted of equiaxed $\alpha_2$ phase. $Ti_3Al-Nb$ alloys and the matix of TiB/(Ti-25Al-11Nb) metal matrix composite had the morphology that O phase was precipitated at the grain boundary of $\alpha_2$phase. Volume fraction of O phase and hardness were depended on the concentration of Nb in $Ti_3Al-Nb$ alloy, Rule of mixing could be applied to hardness and Young's modulus of 18 vol. % TiB/(Ti-25Al-11Nb) metal matrix composite.

• 한국세라믹학회지
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• 제31권5호
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• pp.552-560
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• 1994

A composite of TiB2-Al2O3 system was successfully prepared from a mixture of TiO2, B2O3, and Al by self-propagating high temperature synthesis (SHS) with a novel characteristic, utilizing the internal oxidation heat of aluminium metal of the mixture, instead of by a conventional technique, externally heating a mixture of Ti, B and Al2O3. From a mixture with B/Ti molar ratio of =2.0, pure two phases of TiB2 and $\alpha$-Al2O3 with good crystallinity and small, uniform sizes were formed. However, when the B/Ti molar ratio of the mixture goes to a value less than 2.0, in addition to the above main minerals, a small smounts of metastable phases such as TiB and Ti3B4 were formed. It was found that about 60%, the optimum green density of compacts gave their highest reaction rate and temperature during SHS process. TiB2-Al2O3 system composite with B/Ti molar ratio of =2.0 could be pressurelessly sintered even at 190$0^{\circ}C$ under Ar gas flows without any addition of sintering aids, showing their good properties such as 91.2% in relative density, 2750 kgf/$\textrm{mm}^2$ in Vickers hardness and 2620 kgf/$\textrm{cm}^2$ in flexural strength.

• 한국세라믹학회지
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• 제40권2호
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• pp.128-131
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• 2003

B$_4$C 분말 표면을 알루미나 전구체로 표면 개질하여 알루미늄의 wetting 각을 낮추어 알루미늄의 함침을 용이하게 함으로써 상압에서 B$_4$C/Al 복합체를 제조하고자하였다. 알루미나 전구체에 의한 표면개질은 제타전위의 변화로 확인하였으며, 표면개질된 B$_4$C 분말의 preform에 Al 6061 디스크를 올려놓고 흐르는 알곤 분위기에서 103$0^{\circ}C$/20분 열처리로 Al이 완전히 함침된 B$_4$C/Al 복합체를 제조하였다. 반면 표면 개질되지 않은 B$_4$C 분말은 125$0^{\circ}C$/30분에도 함침이 일어나지 않았다. 이 복합체의 XRD와 SEM 분석은 B$_4$C. Al 외에도 반응상 $Al_3$BC 상이 생성되었으며, 물성을 크게 저하시키는 A1$_4$C$_3$는 생기지 않았음을 보여 주었다.

• 한국세라믹학회지
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• 제33권5호
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• pp.524-530
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• 1996

TiB2-BN-AlN composite was fabricated with the addition of 0~12 wt% WC by HP-sintering. Their sinterability. microstructure mechanical and electrical properties were studied as a function of the WC content. The addition of WC up to 12 wt% increased the flexural strength and decreased electrical resistivity as compared with those of the TiB2-BN-AlN composites. The electrical resistivity of TiB2-BN-AlN composite with 4.3 wt% WC was 640$\mu$$\Omega$-cm. It was found that the TiB2-BN-AlN composites with WC addition more than 4wt% was suitable for the application to the Al evaporation boat.

• 대한금속재료학회지
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• 제49권3호
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• pp.270-274
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• 2011

Plasma electrolytic oxidation (PEO) treatment was performed on squeeze cast AZ31 alloy and $Al_{18}B_4O_{33}w/AZ31$ composite. Scanning electron microscope (SEM) was employed to characterize the surface morphology and cross-section microstructure of the coating. The phase structures of the PEO coating were analyzed by X-ray diffraction (XRD). The corrosion resistance of the PEO coating was evaluated by electrochemical method. The results showed that the $Al_{18}B_4O_{33}$ whisker on the surface of the composite was decomposed and $MgAl_2O_4$ was formed in the PEO coating layer of $Al_{18}B_4O_{33}w/AZ31$ composite during PEO treatment. As a result, the electrochemical corrosion potential of the PEO coated $Al_{18}B_4O_{33}w/AZ31$ composite was increased compared with that of AZ31 alloy.

• 한국세라믹학회지
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• 제40권1호
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• pp.18-23
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• 2003

정량의 B$_2$O$_3$/A1/C의 혼합분말을 화학노 대신 고압의 알곤 분위기를 사용하여 SHS 공정으로 B$_4$C-A1$_2$O$_3$ 복합분말을 제조하였다. 2B$_2$O$_3$+4A1+C=B$_4$C-2A1$_2$O$_3$의 반응식에 해당하는 B$_2$O$_3$(-100 메쉬), Al(-200 메쉬), C(-200 메쉬)의 분말을 2시간 건식 볼밀로 혼합한 후, 고온 고압의 SHS 반응기에 넣고 약 10기압의 알곤 분위기에서 점화하여 SHS을 일으켰다. 반응 생성물은 XRD 분석으로 안과 겉이 균일하게 반응이 일어났으며 반응 생성물로 화학노 사용시 동반되는 부산물 AlB$_{12}$C$_2$가 없는 B$_4$C-A1$_2$O$_3$ 복합 분말을 얻었다. 이 복합 분말은 SEM으로 보면 약 0.3~l $mu extrm{m}$ 크기의 결정이 모인 약 60~100$\mu\textrm{m}$ 크기이었다. 그러나 약 15기압을 사용하였을 때는 부분 소결이 일어나 15~25$\mu\textrm{m}$ B$_4$C 분말에 0.1~0.2$\mu\textrm{m}$의 알루미나가 분산되어 있는 고강도의 복합 분말이 생성되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제10권4호
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• pp.57-66
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• 1986

The microstructure and mechanical properties of unidirectionally solidified Al-Fe-Ni and Al-Fe-B alloys have been studied in varying the some conditions. To investigate the change of microstructure and mechanical properties was carried out by the varying the composition and solidification rate from 1.2 to 80 mm/min at temperature gradient 60 .deg. C/cm. The results obtained are as follow; 1. In proportion to the increase of the solidification rate, the type of crystallized phase of these composite alloys was changed by added element. a) The crystallized phase of composite alloy in added nikel was changed from the rod-type fiber to platetype fiber. b) The crystallized phase of composite alloy in added boron was changed from the plate-type fiber to rod-type fiber. 2. The strength was rapidly increased with the changing process of crystallized fiber from the plate-type fiber to the rod-type.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2000년도 추계학술발표강연 및 논문개요집
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• pp.160-160
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• 2000

• 대한기계학회논문집
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• 제18권7호
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• pp.1713-1721
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• 1994

Intermetallic-matrix composites(IMCs) have the potential of combing matrix properties of oxidation resistance and high temperature stability with reinforcement properties of high specific strength and modulus. One of the major limiting factors for successful applications of these composite at high temperatures is the formation of interfacial reactions between matrix and ceramic reinforcement during composite process and during service. The purpose of the present investigation is to develop a better understanding of the nature of creep fracture mechanisms in a $Ni_{3}Al$ composite reinforced with both $TiB_{2}$ and SiC particulates. Emphasis is placed in the roles of the products of the reactions in determining the creep lifetime of the composite. In the present study, creep rupture specimens were tested under constant ranging from 180 to 350 MPa in vacuum at $760^{\cric}C$. The experimental data reveal that the stress exponent for power law creep for the composite is 3.5, a value close to that for unreinforced $Ni_{3}Al$. The microstructural observations reveal that most of the cavities lie on the grain boundaries of the $Ni_{3}Al$ matrix as opposed to the large $TiB_{2}/Ni_{3}Al$ interfaces, suggesting that cavities nucleate at fine carbides that lie in the $Ni_{3}Al$ grain boundaries as a result of the decomposition of the $SiC_{p}$. This observation accounts for the longer rupture times for the monolicthic $Ni_{3}Al$ as compared to those for the $Ni_{3}Al/SiC_{p}/TiB_{2} IMC$. Finally, it is suggested that creep deformation in matrix appears to dominate the rupture process for monolithic $Ni_{3}Al$, whereas growth and coalescence of cavities appears to dominate the rupture process for the composite.