• Title, Summary, Keyword: NiAl

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Reaction diffusion and formation of$Ni_3Al$ phase at the Ni-NiAl diffusion couple (Ni-NiAl 확산대에서 $Ni_3Al$ 상의 형성과 반응확산)

  • 정승부
    • Journal of Welding and Joining
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    • v.15 no.3
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    • pp.128-135
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    • 1997
  • Reaction diffusion and formation of $Ni_3Al$phase with $L1_2$ structure have been studied in temperature range of 1432K to 1573K using the diffusion couple of (Ni-40, 5at%Al)/(Ni-14, 1at%Al) and (Ni-49, 2at%Al)/ (Nickel). The layer growth of Ni$_{3}$Al pyhase in the annealed diffusion couple was measured by optical microscope and electron probe microanalyzer (EPMA). The layer growth of $Ni_3Al$phase in diffusion zone obeyed the parabolic law without any indication of grain boundary effects. The layer growth of $Ni_3Al$phase in temperature range of 1423K to 1573K was mainly controlled by the volume diffusion mechanism. The rate of layer growth of $Ni_3Al$phase was found to be colsely related to the composition of intermetallic compound NiAl phase. The activation energy for layer growth of $Ni_3Al$phase was calculated to be 127kJ/mol.

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A Study on the Precipitation Behavior of $L2_1$-type Precipitates in B2-NiAl (B2형 NiAl에 석출한 $L2_1$형 석출상의 석출거동에 관한 연구)

  • Han, Chang-Suk;Han, Seung-Oh;Lee, Ju-Hee
    • Journal of the Korean Society for Heat Treatment
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    • v.22 no.6
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    • pp.345-353
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    • 2009
  • The precipitates of $L2_1$-type $Ni_2AlHf$ phase in B2-ordered NiAl system has been observed by using transmission electron microscope (TEM). The hardness of as-quenched NiAl-Hf alloys is high due to the larger strengthening. However, age hardening of this alloy is not main effect to increase hardness compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1$-type $Ni_2AlHf$ precipitates keep a lattice coherency with the NiAl matrix. The orientation relationship between the $Ni_2 AlHf$ precipitate and the NiAl matrix is <100>$_{Ni2AlHf}$//<100>$_{NiAl}$, {001}$_{Ni2AlHf}$//{001}$_{NiAl}$. By aging treatment for long time $Ni_2AlHf$ precipitates lost their coherency and change their morphology to the spherical ones surrounded by misfit dislocations. The orientation relationship between the NiAl matrix and the $Ni_2AlHf$ precipitates, however, has been kept even after longer aging time. The lattice misfit between the $Ni_2AlHf$ precipitate and the NiAl matrix has been calculated by the selected electron diffraction patterns, and the spacings of misfit dislocations is about 4.5% at 1173 K.

Interfacial Reaction of Galvanized Steel in Ni Added Zn-0.18Al Bath (Zn-0.18Al 도금욕에서 Ni첨가에 따른 아연 도금강의 계면반응)

  • 이경구;기회봉;이도재
    • Journal of the Korean institute of surface engineering
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    • v.32 no.4
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    • pp.547-554
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    • 1999
  • The interfacial reaction, spangle and coating thickness of galvanized steel in Ni added Zn-0.18Al bath have been investigated. The size of spangle and thickness of reaction layer were observed under an optical microscope, SEM and EDS. Analysing the experimental results concerning spangle size of galvanized steel it was found that Ni addition in Zn-0.18Al bath tended to be minimized spangle size. For Zn-0.18Al bath, addition of 0.1Ni suppressed the formation of Fe-Zn intermetallic compounds but increased with Ni content above 0.1%. The coating thickness of galvanized steel was reduced with Ni addition in Zn-0.18Al bath, especially in Zn-0.18Al-0.05Ni bath. Addition of Al in Ni containing bath resulted in forming the Al-Ni intermetallic compounds such as $Al_3$Ni$_2$ and $Al_2$Ni which consist most of top precipitates.

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A study on the Microstructure and Mechanical Properties of Two-Phase (($NiAl+Ni_3Al$) 2상 합금의 미세 조직과 기계적 특성에 관한 연구)

  • Lee, Jong-Hun;Choe, Byeong-Hak;Lee, Nam-Jin;Kim, Hak-Min;Lee, Jin-Hyeong
    • 연구논문집
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    • pp.161-174
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    • 1994
  • The Ni-Al intermetallic compound that has the greatest potential to be commercialized shows the high ductility at room temperature with the addition of boron, but has extremely low ductility at high temperature and oxidation environment. On this research work, the changes of microstructure and compressive fracture properties were studied in ($NiAl+Ni_3Al$) two-phase alloys. The precipitation behavior of $Ni_3Al$ after solution treatment at $1300^\circC$ for 14hrs and aging treatment at $800^{\circ}C$ for 14hrs was varied with Al content in ($NiAl+Ni_3Al$) two-phase alloys. These microstructure could be modified dramatically by suitable heat treatments. Martensite or martensite plus $Ni_3Al$ microstructure was obtained upon oil quenching from $1300^\circC$. Aging of Martensite at $800^\circC$ resulted in the $Ni_3Al$ plus NiAl phase. The compressive fracture strength and compressive fracture strain were improved by the $Ni_3Al$ plus NiAl phase mixtures at room temperature and $1100^\circC$. Microcracks are observed mostly in the region of NiAl and the interface of $NiAl-Ni_3Al$ phase after compressive test at room temperature. In the case of high temperature compressive test, microcracks are formed in the region of $Ni_3Al$ phase.

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Effects of Stoichiometry on Properties of NiAl Intermetallics coated on Carbon Steel through Combustion Synthesis (연소합성 코팅된 NiAl 금속간화합물의 화학양론이 미끄럼 마모특성에 미치는 영향)

  • Lee, Han-Young;Lee, Jae-Sung
    • Tribology and Lubricants
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    • v.36 no.3
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    • pp.124-132
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    • 2020
  • The effect of the stoichiometry on the sliding wear properties of NiAl coatings has been investigated. Three different powder mixtures with the compositions of Ni-50at%Al, Ni-54at%Al and Ni-42at%Al were diepressed respectively, and which were subsequently coated on mild steel through combustion synthesis in an induction heating system. Sliding wear behavior of the coatings was examined against an alloyed tool steel using a pin-on-disc type sliding wear test machine. As results, it could be seen that powder mixture(Ni-54at%Al) with displaying Al-rich deviations from the stoichiometry of NiAl(Ni-50at%Al) was promoted the most the synthetic reactivity. The microstructure of the coating layer with the compositions of Ni-54at%Al exhibits the porous NiAl single phase structure. However, the microstructure of the coating layer of the compositions of Ni-42at%Al exhibits the denser multi-phase structure containing several intermediate phases in addition to NiAl. Densification of the coating layer was enhanced by increasing the reacting temperature. On the other hand, the wear properties of the coating layers showed that the wear mode at speeds of around 1 m/s was severe wear, regardless of the stoichiometry and reacting temperature. However, wear properties of coating layer with the compositions of Ni-42at%Al were superior to those of coating layer with the compositions of Ni-54at%Al. This would be attributed by the fact that coating layer with the compositions of Ni-42at%Al develops little void and much intermediate phases with high strength.

Mechanical Properties of Ni Films and $Ni-Al_2O_3$ Composite Films Fabricated by Electroplating (전기도금법으로 제조한 Ni 박막과 $Ni-Al_2O_3$ 복합박막의 기계적 성질)

  • Jun S. W.;Won H. J.;Lee K. Y.;Lee J. H.;Byun J. Y.;Oh T. S.
    • Journal of the Microelectronics and Packaging Society
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    • v.12 no.3
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    • pp.259-265
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    • 2005
  • Characteristics of electroplated Ni films and $Ni-Al_2O_3$ composite films, such as yield strength, fracture elongation, and $Al_2O_3$ content, were evaluated as a function of electroplating current density. $Al_2O_3$ content was $11.48\~11.64\;vol\%$ for $Ni-Al_2O_3$ composite films electroplated at $5\~20\;mA/cm^2$, and decreased to $8.41\;vol\%$ at $30\;mA/cm^2$ $Ni-Al_2O_3$ possessed yield strengths higher than those of Ni films. Especially, $Ni-Al_2O_3$ fabricated at $5\;mA/cm^2$ exhibited $50\%$ improved yield strength. Fracture elongations of Ni and $Ni-Al_2O_3$ decreased with increasing the electroplating current density. $Ni-Al_2O_3$ electroplated at $5\;mA/cm^2$ exhibited more uniform dispersion of $Al_2O_3$ and higher yield strength and larger fracture elongation than the composite films processed at other current densities.

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Phase Decomposition and Strength of B2-Ordered (Ni,Co)Al (B2형 규칙(Ni,Co)Al의 상분리와 강도)

  • Han, Chang-Suck;Kim, Youn-Che
    • Journal of the Korean Society for Heat Treatment
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    • v.9 no.2
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    • pp.79-90
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    • 1996
  • Transmission electron microscopy(TEM) investigation on the phase decomposition of B2-ordered (Ni,Co)Al supersaturated with Ni and Co has revealed the precipitation of $(Ni,Co)_2Al$ which has not been expected from the reported equilibrium phase diagram. The $(Ni,Co)_2Al$ phase has a hexagonal struture and takes a rod-like shape with the long axis of the rod parallel to the <111> directions of the B2 matrix. By aging at temperatures below 873 K, a long period Superlattice Structure appears in the hexagonal $(Ni,Co)_2Al$ Phase. The orientation relationship between the $(Ni,Co)_2Al$ Precipitates and the B2-(Ni,Co)Al matrix is found to be$(0001)_p$ // $(111)_{B2}$ and $[\bar{1}2\bar{1}0]_P$ // $[\bar{1}10]_{B2}$, Where the suffix p and B2 denote the $(Ni,Co)_2Al$ precipitate and the B2-(Ni,Co)Al matrix, respectively. (Ni,Co)Al hardens appreciably by the fine precipitation of the $(Ni,Co)_2Al$ phase. Energy dispersive spectroscopy was used to analyze the compositions of each phase formed in B2-(Ni,Co)Al.

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Crack propagation behavior of in-situ structural gradient Ni/Ni-aluminide//Ti/Ti-aluminide laminate materials (Ni/Ni-aluminide//Ti/Ti-aluminide 구조경사형 층상재료의 균열 전파 거동)

  • Chung, D.S.;Kim, J.K.;Cho, H.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.15 no.6
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    • pp.269-275
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    • 2005
  • Ni/Ni-aluminide/Ti/Ti-aluminide laminate composite, considered as a functionally gradient material, was manufactured by thin foil hot press technique. Thick intermetallic layers of NiAl and $TiAl_3$ were formed by a self-propagating high-temperature synthesis (SHS) reaction, and thin continuous taters of $Ni_3Al$ and TiAl were formed by a solid-state diffusion. Fracture resistance with loading along the crack arrester direction is higher than crack divider direction due to the interruption of crack growth in metal layers. The $Ni_3Al$ and NiAl intermetallic layer showed cleavage and intergranular fracture behavior, respectively, while the fracture mode of $TiAl_3$ layer was found to be an intragranular cleavage. The debonding between metal and intermetallic layer and the pores were observed in the Ni/Ni-aluminide layers, resulting in the lower fracture resistance. With the results of acoustic emission (AE) source characterization the real time of failure and the effect of AE to crack growth could be monitored.

Characterization of Oxide Scales Formed on Fe3Al, Fe3Al-Cr, Fe3Al-Cr-Mo, Ni3Al and Ni3Al-Cr Alloys (Fe3Al, Fe3Al-Cr, Fe3Al-Cr-Mo, Ni3Al 및 Ni3Al-Cr 합금표면에 형성된 산화물 특성분석)

  • Shim, Woung-Shik;Lee, Dong-Bok
    • Korean Journal of Materials Research
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    • v.12 no.11
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    • pp.845-849
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    • 2002
  • Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

Spark-Plasma Sintering of Mechanically-alloyed NiAl Powder and Ball-milled (Ni+Al) Powder Mixture (기계적합금화 NiAl 분말과 볼밀혼합된 (Ni+Al) 분말의 방전플라즈마소결)

  • 장영일;김지순;안인섭;김영도;권영순
    • Journal of Korean Powder Metallurgy Institute
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    • v.7 no.3
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    • pp.161-167
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    • 2000
  • Mechanically-alloyed NiAl powder and ball-milled (Ni+Al) powder mixture were sintered by spark-plasma sintering(SPS) process. Mechanical alloying was performed in a horizontal attritor for 20 h with rotation speed of 600 rpm. (Ni+Al) powder mixtures were prepared by ball milling for 1 and 10 h with 120 rpm. Both powders were sintered at $1150^{\circ}C$ for 5 min under $10^{-3}$ torr vacuum with 50 MPa die pressure in a SPS facility. Sintered densities of 97% and 99% were obtained from mechanically-alloyed NiAl powder and (Ni+Al) powder mixture, respectively. The sintered compact of (Ni+Al) powder mixture showed large grain size by a very rapid grain growth, while the grain size of mechanically-alloyed NiAl powder compact after sintering was extremely fine(80 nm). The difference in densification behavior of both powders were discussed.

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