• 한국주조공학회지
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• 제21권2호
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• pp.127-134
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• 2001

Misch metal (rare earth element, Ce, La, Nd, Pr) which has large influence on high-temperature stability and toughness was added to the Al-5%Ni-5%Mg alloy, and squeeze casting was used for Al-5%Ni-5%Mg-(Mm) alloys. The effect of applied pressure and misch metal additions on mechanical properties in Al-5%Ni-5%Mg alloy by direct squeeze casting has been investigated. The applied pressure were 0 MPa(gravity casting), 25, 50 and 75 MPa. Squeeze-cast Al-5%Ni-5%Mg-(Mm) alloys had better mechanical properties than those of non-pressurized cast alloys because of the increased cooling rate by the application of pressure during solidification. By the addition of misch metal in Al-5%Ni-5%Mg alloy, better combination of strength and elongation was obtained. The addition of 0.3%Mm in Al-5%Ni-5%Mg alloy improved the heat resistant property due to the formation of fine eutectic phases.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.72-75
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• 1998

High temperature deformation behavior of Al85Ni10Y5 alloy extrudates fabricated with amorphous ribbons was investigated at temperature range form 300 to 550$^{\circ}C$ by torsion tests. Thermal properties of amorphous ribbons as a function of aging temperature was studied by Differential Scanning Calorimetry(DSC). The Al phase crystallite firstly formed in the amorphous ribbons and its crystallization temperature(Tx) was ∼210$^{\circ}C$. During the processings of consolidation and extrusion, nano-grained structure was formed in the Al85Ni10Y5 alloy extrudates. The as-extrudated Al85Ni10Y5 alloy and the Al85Ni10Y5 alloy annealed at 250$^{\circ}C$ for 1 hour showed the flow curve of DRV(dynamic recovery) during hot deformation at 400-550$^{\circ}C$. On the other hand, the Al85Ni10Y5 alloy annealed at 400$^{\circ}C$ for 1 hour showed the flow curve of DRX(dynamic recrystallization) during hot deformation at 450-500$^{\circ}C$.

• 한국수소및신에너지학회논문집
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• 제4권1호
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• pp.31-39
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• 1993

In order to improve the hydrogen storage capacity and the activation property of the $MmNi_{4.5}Al_{0.5}$ alloy, the multiphase alloy system are prepared by adding the excess Zr in $MmNi_{4.5}Al_{0.5}$ alloy. It is estimated from the X-ray diffraction pattern and the energy dispersive X-ray analysis that the 2nd phases in $MmNi_{4.5}Al_{0.5}Zr_x$ alloys are $ZrNi_3$, ${\beta}$-Zr. Their morphology is also examined by the scanning electron microscope, and it shows the needle-like precipitation. As the Zr contents increase, the activation time and the plateau pressure decrease, sloping of the plateau pressure increase. Amount of the 2nd phases increase with Zr contents in $MmNi_44.5Al_{0.5}Zr_x$ alloys. The $MmNi_44.5Al_{0.5}Zr_{0.05}$ alloy, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage.

• 소성∙가공
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• 제7권4호
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• pp.333-339
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• 1998

Hot torsion tests were conducted to investigate the high temperature deformation behavior of $Al_{85}Ni_{10}Y_5$ alloy extrudates fabricated with amorphous ribbons. The powder metallurgy routes, hot pressing and hot extrusion were used to fabricate the extrudates. Thermal properties of amorphous ribbons with different thickness as a function of aging temperature were studied by thin film x-ray dif-fraction (XRD) and differential scanning calorimetry(DSC). The Al phase crystallite firstly formed in the amorphous ribbons and its crystallization temperature($T_x$)Was ~210${\circ}C$ During the processings of consolidation and extrusion, nano-grained structure(~100 nm) was formed in the Al85Ni10Y5 alloy extrudates. The as-extrudated Al85Ni10Y5 alloy and the $Al_{85}Ni_{10}Y_5$ alloy annealed at 250${\circ}C$ for 1 hour showed a flow curve of DRV(dynamic recovery) during hot deformation at 400-550${\circ}C$. On the other hand, the $Al_{85}Ni_{10}Y_5$ alloy annealed at 400${\circ}C$ for 1 hour showed a flow curve of DRX(dynamic recrys-tallization) during hot deformation at 450-500${\circ}C$. Also the flow stress and flow strain of the $Al_{85}Ni_{10}Y_5$ alloy extrudate annealed at 400${\circ}C$ were higher than those at 250${\circ}C$.

• 한국재료학회지
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• 제16권2호
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• pp.137-143
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• 2006

The effects of Cu and Fe additions on the thermal stability, microstructure and mechanical properties of $Al_{85}-Ni_{8.5}-Mm_{6.5},\;Al_{84}-Ni_{8.5}-Mm_{6.5}Cu_1,\;Al_{84}-Ni_{8.5}-M_{m6.5}Fe_1$ alloys, manufactured by gas atomization, degassing and hot-extrusion were investigated. Gas atomization, with a wide super-cooled liquid region, allowed the alloy powders to exhibit varying microstructure depending primarily on the powder size and composition. Al hotextruded alloys consisted of homogeneously-distributed fine-grained fcc-Al matrix and intermetallic compounds. A substitution of 1 at.% Al by Cu increased the thermal stability of the amorphous phase and produced alloy microstructure with smaller fcc-Al grains. On the other hand, the same substitution of 1 at.% Al by Fe decreased the stability of the amorphous phase and produced larger fcc-Al grains. The formation of intermetallic compounds such as $Al_3Ni,\;Al_{11}Ce_3\;and\;Al_{11}La_3$ was suppressed by the addition of Cu or Fe. Among the three alloys examined, the highest Vickers hardness and compressive strength were obtained for $Al_{84}-Ni_{8.5}-M_{m6.5}Cu_1$ alloy, and related to the finest fcc-Al grain size attained from increased thermal stability with Cu addition.

• 소성∙가공
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• 제7권5호
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• pp.465-473
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• 1998

The effect of alloying elements of Ag-Cu-Zr-X brazing alloy on the microstructure and the bond strength of $Al_2O_3/Ni-Cr$ brazed steel joint was investigated. The reaction layer, $ZrO_2$ (a=5.146 ${\AA}$ , b=5.213 ${\AA}$ , c=5.311 ${\AA}$ )was formed at the interface of $Al_2O_3/Ni-Cr$ steel joint by the redox reaction between alumina and Zr. The addition of An and Al to the Ag-Cu-Zr brazing alloy gave rise to changes in the thickness of the reaction product layer and the morphology of the brazement. Sn caused the segregation of Zr was decreased b Al the $ZrO_2$ layer formed at the Ag-Cu-Zr-Al alloy was thinner than that of $ZrO_2$ formed at the Ag-Cu-Zr-An alloy. The fracture shear strength was strongly dependent on the microstructure of the brazement. Brazing with Ag-Cu-Zr-Sn alloy resulted in a better bond strength than with Ag-Cu-Zr or Ag-Cu-Zr-Al alloy.

• 열처리공학회지
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• 제15권2호
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• pp.65-69
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• 2002

$Llo{\rightarrow}Ni_5Al_3$ reordering and related properties in Ni-Al alloys consisting of 64-65at%Ni are characterized by X-ray diffraction, shape memory effect and damping capacity. Formation of $Ni_5Al_3$ takes place by simple ordering of atoms with a continuous increase in c/a ratio. As a result, degradation of shape memory effect and damping capacity is observed after short time annealing at $200-300^{\circ}C$.

• 한국수소및신에너지학회논문집
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• 제3권2호
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• pp.45-54
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• 1992

An applicability microencapsulation, using electroless copper plating, of hydrogen storage alloy powder as an anode material for nickel-hydrogen secondary batteries was investigated. Alloys employed were $LaNi_{4.7}Al_{0.3}$ and $MmNi_{4.5}Al_{0.5}$(Mm=mischmetal) which have an appropriate equilibrium pressure and capacity. The microencapsulation of the alloy powder was found to accelerate initial activation of electrodes and to increase capacity which is about 285mAh/g for $LaNi_{4.7}Al_{0.3}$. In addition, other charge and discharge characteristics, such as polarization and flatness of charge and discharge potential, were improved due to the role of copper layer as a microcurrent collector and an oxidation barrier of the alloy powder. $MmNi_{4.5}Al_{0.5}$ alloy showed lower capacity than $LaNi_{4.7}Al_{0.3}$ because of higher equilibrium pressure. Cyclic characteristics of both alloys were somewhat poor because of mainly shedding and partial oxidation of alloy powder during the cycling. However, it was considered that the microencapsulation method is effective to improve the performances of the hydrogen storage alloy electrodes.

• 분석과학
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• 제5권2호
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• pp.203-211
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• 1992

Ni-36.5at.%Al 합금에서 결정립계에서의 scavenging 원소로 알려진 V를 첨가하여 이 합금의 파괴거동 및 마르텐사이트 미세조직에 미치는 V의 영향에 대해 조사하였다. 시편의 파단면은 주사전자현미경으로 관찰하였고 EDX spectrometer를 사용하여 파단면의 조성을 분석하였으며 투과전자현미경으로 마르텐사이트 내부조직의 변화에 대해 조사하였다. V의 첨가로 입계파괴에서 입내파괴로 파괴 모드의 변화를 나타내었으며 EDX spectrometer로 분석한 결과 입내에 비해 입계에 Al의 함량이 상대적으로 증가되는 양상을 보여 주었다. Ni-36.5at.%Al 합금의 경우 마르텐사이트 플레이트는 내부쌍정으로 이루어져 있으나 V의 첨가에 따라 twinned 마르텐사이트 조직은 사라지며 stacking fault와 고밀도의 전위를 가진 modulated 조직이 점차 지배적으로 형성되는 것이 관찰되었다. Stacking fault를 분석한 결과 Al과 V의 치환에 따른 extrinsic fault였으며 high-energy 상태인 이 stacking fault가 있는 부위에 유해 원소인 S가 편석됨으로써 결정립계에서의 파괴를 줄일 수 있었다.

• 소성∙가공
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• 제8권6호
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• pp.626-633
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• 1999

$Al_{85}Ni_{10}Y_5$ (at. %) amorphous alloy ribbons have been produced by rapidly solidification process and consolidated by the conventional powder metallurgy method. The grains with ∼90 nm were obtained in the Al85Ni10Y5 alloy extrudates by hot-pressing followed by hot-extusion. To investigate the effect of heat treatment on microstructural change of the extrudates, heat treatment was carried out from 200℃ to 400℃ at the step of 50℃. In addition, mechanical properties of the extrudates were analysed from torsion test at the temperature range or 400∼500℃ under a strain rates of 0.2, 0.5, and 1.0/sec. The extrudates showed a flow stress of ∼190 MPa and low elongation of ∼150% at 400℃, contributing to the enhancement of ductility and hardness for extrudates. Also, grain boundary sliding was occurred in the $Al_{85}Ni_{10}Y_5$ alloy during hot deformation.