• Journal of the Korean Society for Heat Treatment
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• v.9 no.4
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• pp.243-251
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• 1996

Dilatometric experiment and thermodynamic calculation have been performed to determine $M_s$, $A_s$ and driving forces for ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation of Fe-Mn alloys. The transformation temperatures($M_s$, $A_s$, $T_o) were decreased with increasing manganese content and were newly formulated as a function of manganese content. Driving force for ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation was increased from -75J/mole to -105J/mole with increasing manganese content from 15wt.% to 25wt.%. Transformation temperature hysteresis($A_s-M_s$) was also increased from 50K to 80K with increasing mangenese content from 15wt.% to 25wt.%. The small driving force(-75J/mole~-105J/mole) and small ${\Delta}T$(50K~80K) for ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation indicated that Fe-Mn alloys behave like thermoelastic martensitic alloys : We would like to call them semi-thermoelastic martensitic alloys.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.967-976
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• 1995

The possiblity of the existence of a spontaneous relaxor-normal ferroelectric transition was proposed and examined using 1~5 mol% PbZrO3-doped Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) systems having tetragonal symmetry at rom temperature. On cooling, the system with 60mol% Pb(Ni1/3Nb2/3)O3 underwent a spontaneous transition from a relaxor to a normal ferroelectric state. A microscopic examination demonstrates that the relaxornormal ferroelectric transition corresponds to a micro-macro domain switching accompanied with thermoelastic martensitic transformation. The long-range macrodomains below the transition temperature were characterized by twinlike 90$^{\circ}$macrodomains with tetragonal symmetry. The relaxor-normal ferroelectric transition was further correlated with the rhombohedral-tetragonal first-order structural transition.

• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.8-13
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• 2015

The magnetic shape memory alloys have recently received a lot of attention due to the considerable progress achieved in understanding the particular importance and the development of the factors. Among these alloys, the ferromagnetic Co-Ni- alloys have been concerned specially because of the thermoelastic character of the fcc (g) - bct (a) martensitic transformation which exhibits under the action of the temperature (shape memory effect), the stress (superelasticity) and the magnetic field (magnetoelasticity). The morphological, the crystallographical, and the thermal characteristics of thermally induced martensite in Co-35.3Ni-11.3Al(wt.%) and Co-28.1Ni-47.4Fe-3.3Ti (wt.%) alloy have been investigated by the scanning electron microscope (SEM), the X-ray Diffraction (XRD), and the differential scanning calorimeter (DSC).