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한창석,김윤채 ( Chang Suck Han,Youn Che Kim ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.2
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> directlions of the B2 matrix. By aging at temperatures below 873K, 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 [1 ̄21 ̄0]_P // [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.
B2형 금속간화합물 β-NiAl중에 α-Cr입자의 석출거동
한창석,김윤채 ( Chang Suck Han,Youn Che Kim ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.2
Microstructural control to produce multiphase structure has received much attention to improve the high temperature strength as well as low temperature ductility of intermetallics. Transmission electron microscopic investigation has been carried out concerning the effect of Cr-precipitation on the mechanical properties of B2-ordered NiAl containing 4 to 8 mold% of Cr. By aging at temperatures around 973K after solution annealing, fine spherical precipitates took place homogeneously in the NiAl matrix and the alloys hardened appreciably. Selected area electron diffraction(SAED) patterns have not revealed any additional extra-spots during aging, because the Cr-particles show cube-cube orientation relationship and keep a perfect coherency with the ordered matrix lattice. Dislocations were confirmed to bypass the particles during deformation. Although the dispersion of Cr-particles increased the yield strength of NiAl at intermediate temperature, the strength decreased appreciably at higher temperatures.
석출강화된 Ni3(Al , Cr)-C계에서의 전위-석출입자간의 상호작용
한창석 ( Chang Suck Han ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.1
The morphology of deformation induced dislocations in polycrystalline Ni₃(Al, Cr) containing M_(23)C_6 precipitates has been investigated in terms of transmission electron microscopy(TEM). Fine Polyhedral precipitates of M_(23)C_6 appeared in the matrix by aging at temperatures around 973 K after solution annealing at 1423 K. TEM examination revealed that the M_(23)C_6 phase and the matrix lattices have a cube-cube orientation relationship and keep partial atomic matching at the {111} interface. After deformation at temperature below 973 K, typical Orowan loops were observed surrounding the M_(23)C_6 particles. At higher deformation temperatures, the Orowan loops disappeared and the morphology of dislocations at the particle-matrix interfaces suggested the existence of attractive interaction between dislocations and particles. The change of the interaction modes between dislocation and particles with increasing deformation temperature can be considered as a result of strain relaxation at the interface between matrix and particles.
Ll2-규칙 Ni3 (Al , Cr) 중에 M23C6형 carbide의 석출
한창석 ( Chang Suck Han ),김윤채 ( Youn Che Kim ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.3
Structural studies have been performed on precipitation hardening discovered in Ll₂-ordered Ni₃(Al, Cr) containing 0.2 and 0.5 ㏖% of carbon in terms of transmission electron microscopy(TEM). By aging at temperatures around 1073 K after solution treatment at 1423 K, fine polyhedral precipitates appear firstly on the dislocations and then in the matrix. The selected area electron diffraction (SAED) studies revealed that these particles are a M_(23)C_6 type carbide which has the cube-cube orientation relationship with the matrix lattice. Weak-beam electron microscopy observations of deformation induced dislocations suggested that the dislocations bypass the carbide particles during deformation.
조성욱(Sung Wook Cho),한창석(Chang Suck Han),박충년(Choong Nyeon Park) 한국수소및신에너지학회 1998 한국수소 및 신에너지학회논문집 Vol.9 No.3
The change of hydrogen storage characteristics by substituting zirconium for a portion of titanium in Ti-Cr-V alloys has been studied. The zirconium substitution decreased the plateau pressure and hysteresis of the PC isotherm. However, it decreased the hydrogen storage capacity and increased slopping in PC isotherm by forming Cr₂Zr phase. By modifying the composition ratio of titanium to chromium, thereby suppressing the formation of Cr₂Zr phase, we got an alloy having very high hydrogen storage capacity. The heat treatment of the alloys improved the flatness of plateau very much without a decrease in the maximum and the effective hydrogen storage capacities.
조성욱(Sung Wook Cho),한창석(Chang Suck Han),박충년(Choong Nyeon Park) 한국수소및신에너지학회 1998 한국수소 및 신에너지학회논문집 Vol.9 No.1
The crystal structures, the lattice parameters and the characteristics of hydrogen storage at 303K has been investigated in the ternary alloys of Ti-Cr-V system. All of these alloys, in the range of this study, have shown a bcc structure. The hydrogen storage capacities and the effective hydrogen storage capacities of the alloys were strongly dependant on the composition ratio of Ti/Cr, showing their maximum values at the Ti/Cr ratio of about 0.75. It was also found that the lattice parameters of the alloys increased linearly with an increase of the Ti/Cr ratio. The differences in affinities to hydrogen and lattice parameters of pure metal states of the three elements have been adopted in odor to explain the Ti/Cr ratio dependance of the lattice parameter and hydrogen storage capacity of the alloys.