• 한국분말재료학회지
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• 제3권1호
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• pp.42-48
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• 1996

To investigate the phase transformation behaviors of mechanically alloyed Nb-25 at%Al powders, the mixed Nb-25 at%Al powders were mechanically alloyed in SPEX 8000 Mixer/Mill. Mechanical alloying(MA) time was varied between 0.5 hour and 72 hours. The phase formation behaviors of these mechanically alloyed powders were examined using X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and differential thermal analysis(DTA). Appreciable amorphization started from 6 hours of MA. The powders mechanically alloyed for 10 hours were in almost amorphous phase. DTA results showed that the powders mechanically alloyed for 12 hours had a strong exothermic peak about$600^{\circ}C$, whereas the powders mechanically alloyed for 6 hours had two exothermic peaks. The first peak was found to be due to the stress relief effect and the second one due to the formation of$Nb_{3}Al,Nb_{2}Al and Nb_{2}C$phases by crystallization.

• 한국분말재료학회지
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• 제4권3호
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• pp.205-213
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• 1997

Mechanical alloying of $Ni_3Al$ and $Y_2O_3$ added ODS $Ni_3Al$ from elemental powders was investigated by the X-ray diffraction, differential scanning calorimeter, transmission electron microscopy and optical microscopy. The steady states of $Ni_3Al$ and ODS $Ni_3Al$ powders were reached after mechanical alloying with the condition of the ball-to-powder input ratio of 20:1 for 20 hours and 10 hours, respectively. The addition of nano-sized $Y_2O_3$ particles enhanced cold working and fracture, and subsequently accelerated MA of $Ni_3Al$ powders. DSC results of MAed $Ni_3Al$ powders showed four exothermic peaks at 14$0^{\circ}C$, 234$^{\circ}C$, 337$^{\circ}C$ and 385$^{\circ}C$. From the high temperature X-ray diffraction analysis, it was concluded that the peaks were resulted from the recovery solution of unalloyed Al in Ni, the formation of intermediate phase NiAl, and $LI_2$ ordering of MAed $Ni_3Al$ powders.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2012년도 자성 및 자성재료 국제학술대회
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• pp.130-131
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• 2012

In this study, the thermodynamic and magnetic properties of alloying element substituted B2 FeAl systems have been investigated using the all-electron FLAPW method based on the GGA. It was shown that the important changes take place in the structural properties as well as in the magnetism when alloying element is substituted by Fe or Al site in B2 FeAl. Detailed discussion on the thermodynamic and magnetic properties and electronic structure of these intermetallic compounds will be given.

• 한국재료학회지
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• 제16권9호
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• pp.584-591
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• 2006

To enhance the machinability of the austenite stainless alloys, Mn and S were added to form MnS in the austenite matrix. Recently, Ca is also added to increase machinability. The alloying elements, such as C, Mn, S, Ca, and Al, are known to affect machinability, but those roles are not well understood. In this study, the ingots, controlled of alloying elements, C, Mn, S, Ca, Al, were prepared in the 304 stainless steel. The relationship between microstructure and machinability was compared to understand the role of alloying elements. It was proved that Mn and S enhanced machinability but C reduced it by analyzing cutting force on machining in the lathe. The alloying elements, Ca and Al, made a complex oxide compound of Mn-S-Ca-Al-Si-O, which results in increasing tool life. The ferrite volume fraction was changed with alloying elements and the effect of the ferrite fraction on machining was also discussed.

• 한국결정성장학회지
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• 제23권6호
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• pp.314-319
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• 2013

본 연구에서는 $Fe_2O_3-Al$계 나노복합재료를 제조하기 위하여 실온 기계적 합금화법(MA)을 적용하였다. $Fe_2O_3$와 순금속 Al의 혼합분말을 5시간 동안 MA 처리한 결과 ${\alpha}-Fe$ 기지에 $Al_2O_3$가 미세하게 분산된 ${\alpha}-Fe/Al_2O_3$ 나노복합분말을 얻을 수 있었다. 또한 MA 분말의 자화값 및 보자력 측정을 통하여 볼밀처리 중 순금속 Al에 의한 헤마타이트의 고상환원 과정을 자세히 관찰할 수 있었다. MA 분말시료의 벌크화를 위하여 소결온도 $1000^{\circ}C$ 및 $1100^{\circ}C$, 압력 60 MPa 에서 SPS 소결을 실시하였다. SPS 과정에서 MA 5시간 시료의 수축은 소결 개시 후 $700^{\circ}C$ 이상에서 크며 소결온도 $1100^{\circ}C$까지 비교적 단조롭게 수축함을 알 수 있었다. X선 회절 결과로부터, MA 분말을 $1100^{\circ}C$에서 SPS 소결시킨 ${\alpha}-Fe/Al_2O_3$ 나노복합재료의 경우 ${\alpha}-Fe$상 평균 결정립 크기가 180 nm임을 알 수 있었다. 또한 MA 분말을 $1000^{\circ}C$에서 SPS 소결시킨 시료의 보자력이 88 Oe로 여전히 높은 값을 보이는 사실로부터 소결과정 중 자성상 ${\alpha}-Fe$의 결정립 성장이 크게 억제된 것으로 판단된다.

• 한국표면공학회지
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• 제54권5호
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• pp.285-293
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• 2021

High-entropy TiAlCrSiN nano-composite coating was designed to improve mold life for high temperature liquid molding. Alloy design, powder fabrication and single alloying target fabrication for the high-entropy nano-composite coating were carried out. Using the single alloying target, an arc ion plating method was applied to prepare a TiAlCrSiN nano-composite coating had a 30 nm TiAlCrSiN layers are deposited layer by layer, and form about 4 ㎛-thickness of multi-layered coating. TiAlCrSiN nano-composite coating had a high hardness of about 39.9 GPa and a low coefficient of friction of less than about 0.47 in a dry environment. In addition, there was no change in the structure of the coating after the dissolution loss test in the molten metal at a temperature of about 1100 degrees.

• 소성∙가공
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• 제28권1호
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• pp.34-42
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• 2019

In this study, various alloying elements (Cr, Sr, Ca, Cd) were added to improve the mechanical properties of ADC12 fabricated by a die casting process. The effect of alloying elements on the microstructure and mechanical properties were investigated. The phase analysis results of the modified ADC12 alloy with conventional ADC12 alloy, showed the similar characteristics of Al matrix, Si phase, $CuAl_2$ phase and the Fe intermetallic phase. As a result of the microstructure observation, the secondary dendrite arm spacing (SDAS) was shown to have decreased after the addition of the alloying elements. The eutectic Si phase, which existed as flake form in the conventional ADC12 alloy, was modified finely as a fiber form in the modified ADC12 alloy. It was observed that the $CuAl_2$ phase as the strengthening phase was relatively finely distributed in the modified ADC12 alloy. The Fe intermetallic appeared as a Chinese script shaped $Al_6$ (Mn,Fe) which is detrimental to mechanical properties in conventional ADC12 alloy. On the other hand, in the modified ADC12 alloy, polyhedral ${\alpha}-Al_{15}Si_2$ $(Fe,Mn,Cr)_3$ was observed. The tensile properties were improved in the modified ADC12 alloy. The yield strength and tensile strength increased by 12.4% and 10.0%, respectively, in the modified ADC12 alloy, and the elongation was also seen to have been increased. As a result of the pin on disk wear test, the wear resistance properties were also improved by up to about 7% in the modified ADC12 alloy. It is noted that the wear deformation microstructures were also observed, and it was found that the fine eutectic Si and strengthening phases greatly improved abrasion resistance.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.458-464
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• 2011

Recently, one of the hydrogen production methods has attracted using dense metallic membrane. It has high hydrogen permeation and selectivity which hardly could adopt industrial product because of high cost, hydrogen embrittlment and thermal stability. Meanwhile, vanadium has high hydrogen solubility and it use to instead of Pd-Ag amorphous membrane. Aluminum carried out blocking hydrogen diffusion on grain boundary therefore protecting hydrogen embrittlement. Most of dense metallic membrane is solution diffusion mechanism. The solution diffusion mechanism was very similar hydrogen storing steps such as steps of metal hydride. Thus, V-Al composites were fabricated to use hydrogen induced mechanical alloying. The fabricated V-Al composites were characterized by XRD, SEM, EDS and simultaneous TG/DSC analyses. The hydrogenation behaviors were evaluated using a Sievert's type automatic PCT apparatus. The hydrogenation behaviors of V-Al composites was evaluated too low hydrogen stored capacity and fast hydrogenation kinetics. In PCI results, V-Al composites had low hydrogen solubility, in spite of that, hydrogen kinetics was calculated very fast and hydrogen absorption/desorption contents were same capacity.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.729-730
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• 2006

The research involves the development of a powder metallurgical route for producing good quality TiAl targets for making physical vapour deposition (PVD) coatings. Mixtures of elemental titanium and aluminium powders were mechanically milled using a novel discus milling technique under various conditions. Hot isotropic pressing (HIP) was then employed for consolidation of the mechanically alloyed powders. A cathodic arc vapour deposition process was applied to produce a TiAlN coating. Microstructural examination was conducted on the target material and PVD coatings, using X-ray diffractometry (XRD), X-ray photoelectron spectrometry (XPS) and scanning electron microscopy (SEM). It has been found that combining mechanical alloying and HIP enable us to produce fairly good quality of TiAl based target. The PVD coatings obtained from the TiAl target showed very high microhardness values.

• 한국주조공학회지
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• 제15권4호
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• pp.416-421
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• 1995

Recently Al-Cu-P alloys are used to refine primary Si of hypereutectic Al-Si alloys. Because it has inside AlP compound that acts as nucleation site in the melt, Al-Cu-P alloy has good refinement effect in lower holding temperature and after shoter holding times. In this study Al-Cu-P refinement agent was made by mechanical alloying method. When Al-13.5wt%Cu-1.5wt%P was alloyed mechanically for 30hr in Ar atmosphere by high energy ball mill, it had the refinement effect that showed primary Si size of about $30{\mu}m$ in Al-20wt%Si at $760^{\circ}C$, treated for 15min.