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A Study on the Creep Strength of L12 and B2-ordered Intermetallics
한성오,한창석 대한금속·재료학회 2010 대한금속·재료학회지 Vol.48 No.12
The creep rates of polycrystalline L12-ordered Co3Ti and B2-ordered NiAl-Hf intermetallics decrease appreciably with the fine precipitation of the coherent disordered fcc Co-rich phase and Ni2AlHf phase. With B2-ordered NiAl containing L21-Ni2AlHf precipitates, transmission electron microscope observations of the interaction between dislocations and spherical precipitates revealed that the dislocations tend to be strongly attracted to the particle interfaces during the creep deformation. On the other hand, with L12-ordered Co3Ti, the significance of the threshold stress is discussed based upon the transmission electron microscope observations of the interaction between dislocations and precipitates. The superdislocations produced during deformation tend to be strongly attracted and dissociated as they meet the coherent disordered precipitates because the anti-phase boundary energy in the disordered phase was zero. An extra force required to pull the dislocations out of the disordered particles during the creep deformation establishes the threshold stress which is beneficial for improving creep strength under lower stresses.
한성오(SONG HO HAN),민원근(WON LEUN MIN) 강원대학교 기초과학연구소 1984 기초과학연구 Vol.1 No.-
이 논문에서는, 극소 변환군 위에서의 endomorplism에 대해 연구하였으며, (X, T),(Y, T)가 주어진 극소변환군이고, A(X)와 A(Y)가 algebraiclly tromsitive 하면 다음이 성립한다. φ : (X, T)→(Y, T)가 distal homomorphism이면 필요충분하게 θ : (E(X),T)→(E(Y), T)가 distal epimorphism이다. In this paper, We study for endomorphisms of minimal transformation group. In particular, we stusy the following thing : Let(X, T) and (Y, T) be minimal transformation groups, and let A(X) and A(Y) be both algebraically transitive. Then φ : (X , T)→(Y , T) is distal homomorphism if am only if θ : (E(X),T)→(E(Y), T)is distal epimorphism.
The Behavior of α-Cr Precipitation on the High Temperature Deformation of B2-Ordered NiAl
한창석,전창환,한성오 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.2
Transmission electron microscope investigation has been performed concerning the effect of Cr-precipitation on the mechanical properties of B2-ordered NiAl containing 4 mol.% to 8 mol.% of Cr. By aging at temperatures around 973 K after solution annealing, fine spherical precipitates appeared homogeneously in the NiAl matrix and the alloys hardened appreciably. The selected area electron diffraction patterns have not revealed any additional extra-spots during aging, because the Cr-particles have a cube-cube orientation relationship and keep perfect coherency with the ordered matrix lattice. Dislocations bypass the particles during deformation. Although the dispersion of Cr-particles increases the yield strength of NiAl at intermediate temperature, the strength decreases appreciably at higher temperatures. Atom location by channeling enhanced microanalysis technique has been used to determine the site occupancy of Cr in NiAl. Transmission electron microscope investigation has been performed concerning the effect of Cr-precipitation on the mechanical properties of B2-ordered NiAl containing 4 mol.% to 8 mol.% of Cr. By aging at temperatures around 973 K after solution annealing, fine spherical precipitates appeared homogeneously in the NiAl matrix and the alloys hardened appreciably. The selected area electron diffraction patterns have not revealed any additional extra-spots during aging, because the Cr-particles have a cube-cube orientation relationship and keep perfect coherency with the ordered matrix lattice. Dislocations bypass the particles during deformation. Although the dispersion of Cr-particles increases the yield strength of NiAl at intermediate temperature, the strength decreases appreciably at higher temperatures. Atom location by channeling enhanced microanalysis technique has been used to determine the site occupancy of Cr in NiAl.