• 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.

• 연구논문집
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• s.24
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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.

• 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.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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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.

• Clean Technology
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• v.28 no.2
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• pp.154-162
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• 2022

Microstructured Al@Al₂O₃ and Al@Ni-Al LDH (LDH = layered double hydroxide) core-shell metal-ceramic composites are prepared by hydrothermal reactions of aluminum (Al) metal substrates. Controlled hydrothermal reactions of Al metal substrates induce the hydrothermal dissolution of Al ions at the Al-substrate/solution interface and reconstruction as porous metal-hydroxides on the Al substrate, thereby constructing unique metal-ceramic core-shell composite structures. The morphology, composition, and crystal structure of the core-shell composites are affected largely by the ions in the hydrothermal solution; therefore, the critical physicochemical and surface properties of these unique metal-ceramic core-shell microstructures can be modulated effectively by varying the solution composition. A Ni/Al@Al₂O₃ catalyst with highly dispersed catalytic Ni nanoparticles on an Al@Al₂O₃ core-shell substrate was prepared by a controlled reduction of an Al@Ni-Al LDH core-shell prepared by hydrothermal reactions of Al in nickel nitrate solution. The reduction of Al@Ni-Al LDH leads to the exolution of Ni ions from the LDH shell, thereby constructing the Ni nanoparticles dispersed on the Al@Al₂O₃. The catalytic properties of the Ni/Al@Al₂O₃ catalyst were investigated for CO₂ methanation reactions. The Ni/Al@Al₂O₃ catalyst exhibited 2 times greater CO₂ conversion than a Ni/Al₂O₃ catalyst prepared by conventional incipient wetness impregnation and showed high structural stability. These results demonstrate the high effectiveness of the design and synthesis methods for the metal-ceramic composite catalysts derived by hydrothermal reactions of Al metal substrates.

• 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.

• Journal of Powder Materials
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• v.10 no.3
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• pp.195-200
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• 2003

Ni coated $Al_2O_3$ composite was successfully Prepared by the electroless deposition Process. The average size of Ni particles coated on the $Al_2O_3$ matrix powder was about 20 nm. It was hard to find any reaction compound as an impurity at interface between $Al_2O_3$ and Ni particles after sintering. The characterization of microstructure crystal structure and fracture behavior of the sintered body were investigated using XRD, TEM and Victors hardness tester, and compared with those of the sintered $Al_2O_3$ monolithic body. Many dislocations were observed in the Ni phase due to the difference of thermal expansion coefficient between $Al_2O_3$ and Ni phase, and no observed microcracks at their $Al_2O_3$ and Ni interface. In the $Al_2O_3$/Ni composite, the main fracture mode showed a mixed fracture with intergranular and transgranuluar type having some ,surface roughness. The fracture toughness was slightly increased due to the plastic deformation mechanism of Ni phase in the $Al_2O_3$/Ni composite.

• Journal of Powder Materials
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• v.4 no.3
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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.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.167-172
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• 2016

The high temperature deformation behavior of $Ni_3Al$ and $Ni_3(Al,Mo)$ single crystals that were oriented near <112> was investigated at low strain rates in the temperature range above the flow stress peak temperature. Three types of behavior were found under the present experimental conditions. In the relatively high strain rate region, the strain rate dependence of the flow stress is small, and the deformation may be controlled by the dislocation glide mainly on the {001} slip plane in both crystals. At low strain rates, the octahedral glide is still active in $Ni_3Al$ above the peak temperature, but the active slip system in $Ni_3(Al,Mo)$ changes from octahedral glide to cube glide at the peak temperature. These results suggest that the deformation rate controlling mechanism of $Ni_3Al$ is viscous glide of dislocations by the <110>{111} slip, whereas that of $Ni_3(Al,Mo)$ is a recovery process of dislocation climb in the substructures formed by the <110>{001} slip. The results of TEM observation show that the characteristics of dislocation structures are uniform distribution in $Ni_3Al$ and subboundary formation in $Ni_3(Al,Mo)$. Activation energies for deformation in $Ni_3Al$ and $Ni_3(Al,Mo)$ were obtained in the low strain rate region. The values of the activation energy are 360 kJ/mol for $Ni_3Al$ and 300 kJ/mol for $Ni_3(Al,Mo)$.

• Composites Research
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• v.16 no.3
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• pp.68-74
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• 2003

In this paper, intermetallic/metal laminated composites have been successfully produced that utilizes SHS reactions between Ni and Al elemental metal foils. The reaction between Ni and Al started from the nucleation and growth of NiA1$_3$ and was followed by the diffusional growth of Ni$_2$A1$_3$ between Ni and NiA1$_3$. The SHS reaction was thermodynamically analyzed through the final volume fraction of the non-reacted Al related with the initial thickness ratio of Ni:Al and prior heat treatment. Thermally aging these 1aminates resulted in formation of a functionally gradient series of intermetallic phases. Microstructure showed that the intermetallic volume percent was 82, 59.5, 40% in the 1:1, 2:1, 4:1 thickness ratio specimen. Main phases of the intermetallic were NiAl and Ni$_3$Al having higher strength at room and high temperatures.