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Fe-Cr-Mn제진합금의 감쇠능미치는 합금원소 및 서브제로처리의영향
조덕호(D. H. Cho),남기우(K. Woo. Nam),강창룡(C. Y. Kang) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11
The Effect of addition of Co, N ana subzero treatment on tensile strength and damping capacity were investigated in Fe-Cr-Mn alloy. Austenite was transformed to martensite by cold rolling and with increasing degree of cold rolling, volume fraction of martensite was increased. Damping capacity was linearly increased with increasing volume fraction of e martensite in cold rolled specimens and subzero treated specimen after cold rolling. Volume fraction of e martensite, elongation and damping capacity was increased by Co addition, and tensile strength was decreased, while, c martensite, elongation and damping capacity decreased and tesite strength was increased by N addition. Tensile strength and damping capacity was increased and elongation was decreased by subzero treatment.
Mn - Zn Ferrites의 자기적 성질에 미치는 V₂O5의 첨가효과
조덕호(D. H. Cho) 한국자기학회 1992 韓國磁氣學會誌 Vol.2 No.3
The effects of V₂O_5, addition as an additive on the densification, the microstructure and the magnetic properties of Mn-Zn ferrites were studied. The maximum density was observed at 0.1 wt% V₂O_5, content and it was recognized that a small content of V₂O_5, prohibited the discontinuous grain growth. The initial permeability showed maximum at 0.1 wt% V₂O_5, content and the power loss minimum at 0.03 wt% V₂O_5, content. It was found that a small content of V₂O_5 went into solid solution in the Mn-Zn ferrites, but above that extent V₂O_5, formed a second phase to be segregated at the grain boundaries.
Co 치환이 α-Fe기 초미세결정립 Nd - Fe - B계 합금의 자기특성에 미치는 영향
조덕호(D. H. Cho),조용수(Y. S. Cho) 한국자기학회 2002 韓國磁氣學會誌 Vol.12 No.1
The Effects of Co-substitution in the nanocrystalline Nd-Fe-B-Mo-Cu alloys were investigated. α-Fe based nanocrystalline Nd-Fe-B-Mo-Cu alloys were prepared by crystallization process of amorphous Nd-Fe-B-Mo-Cu alloy produced by rapid solidification process. The substitution of Co resulted in the decrease of grain size and improves the hard magnetic properties. The remanence, coercivity, and Curie temperature of nanocrystalline Nd₄(Fe._(85)Co._(15))_(82)B_(10)Mo₃Cu alloy showed more improved magnetic properties than those of Co-free alloy. The grain size was measured to be about 15 ㎚. The coercivity, remanence and maximum energy product were 239 ㎄/m, 1.4 T, and 103.5 kJ/㎥, respectively, for the nanocrystalline Nd₄(Fe_(0.85)Co_(0.15))_(82)B_(10)Mo₃Cu alloy annealed for 0.6 ks at 640℃.
전호병,조덕호,이형복,박성,Jun, H.B.,Cho, D.H.,Lee, H.B.,Park, S. 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.10
We powders were synthesized from W powders in differnet particle sizes by Self-propagating High-temperature Synthesis process (SHS) using a chemical furnace. The effects of the mole ratio of chemical fuel content, pellet thickness and the mole ratio between carbon and tungsten (C/W Ratio) on synthesis were investigated with the tungsten powders have different particle size each other. Compositional and structural characterization of these powders was carried out by scanning electron microscope (SEM0 and x-ray diffractometer. Powder characterization was carried out by the measurement of particle size distribution with laser-particle size analyzer. The amounts of WC obtained by SHS process depend very much on the particle size of tungsten powder and heat contents given in a product, i.e. as the particle size of W powder is smaller, the amounts of WC produced increase. Also the more heat contents is given, the more amounts of WC increase. By optimizing the synthesis conditions, it is possible to fabricate WC powders which have little secondary phases (W2C, C).
SHS 화학로법에 의해 합성된 WC 분말과 상용 WC 분말을 이용한 $WC-Co-Al_2O_3$ 세라믹 복합체의 제조 및 그 기계적 특성에 관한 연구
이강렬,조덕호,이형복,박성,Lee, K.R.,Cho, D.H.,Lee, H.B.,Park, S. 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.12
WC-10wt%Co-Al2O3 ceramic composites, using both the SHS (Self-propagating High Temperature Synthesis) synthesized WC powder method and commercial WC powder, were prepared by varing WC-Co/Al2O3 vol% ratio and sintering temperature (1350℃∼1650℃) for 1 hr in Ar atmosphere. Mechanical characterization has been investigated by Instron meterial testing system and Vicker's hardness test. Compositional and structural chracterizations were carried out by energy-dispersive analysis of X-ray (EDAX) data and scanning electron microscope (SEM). Electrical characterization was carried out by the electrical resistivity measurement using 4-point probe method. As sintering period increased and Al2O3 contents decreased in WC-10wt%Co-Al2O3 ceramic composite, shrinkage and relative density increased, resulting in maximum values at 1600℃. Also the major matrix phase changed with increasing Al2O3 content from 0 to 100 vol%. It was also identified by SEM, EDAX, and electrical resistivity measurement. Based on the results of analysis of flexural strength, toughness and hardness, the mechanical properties of WC-10wt%Co-Al2O3 ceramic composites using the SHS synthesized WC powder were better than those WC-10wt%Co-Al2O3 ceramic composites using commercial WC powder because WC-10wt%Co-Al2O3 ceramic composites using the SHS synthesized WC powder were sintered very well due to small initial particle size. By the addition of 40 vol% Al2O3 [60(WC=10wt%Co)-40Al2O3], it was possible to obtain a proper candidate as a superalloy.
Fe-28Mn-2Al-3Si 합금의 진동 감쇠능에 관한 연구
권민기(M. K. Kwon),박영태(Y. T. Park),조덕호(D. H. Cho),강창룡(C. Y. Kang) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The effect of the damping capacity of Fe-28Mn-2Al-3Si alloy has been investigated after changing the microstructure by cold rolling. Microstructures in Fe-28Mn-2Al-3Si at room temperature consist of a large quantity of austenite and small quantities of ε and α' martensites. And ε and α' martensites were increased by increasing the degree of cold rolling. With increasing the grain size, the volume fraction of martensite was increased which transformed from the austenite by the cold rolling. Damping capacity was linearly increased with increasing the degree of rolling due to transforming austenite to martensite by deformation. Damping capacity is strongly affected by ε martensite than α' martensite making by deformation induced martensite.
MnZn ferrite의 자기적 성질에 미치는 하소조건의 영향(2)
조덕호 大田産業大學校 1996 한밭대학교 논문집 Vol.13 No.1
In this study, preparing the specimens of MnZn ferrites with the chemical composition of zero magnetostriction and zero magnetic anisotropy, we investigated the effects of the calcining conditions on the magnetic properties of MnZn ferrites. The results obtained from this study are as follows : The saturation magnetization of sintered MnZn ferrites increases a little along with the calcining temperature, and the electrical resistivity of the ferrites increases with the calcining temperature to reach maximum value at about 900℃. The initial permeability, measured at 20℃, increases with the calcining temperature to reach maximum value at around 900℃, but successively decreases above 900℃. The coercive force decreases up to around 900℃, whereafter it successively increases with the calcining temperature. The power loss appears constant up to 900℃ with the calcining temperature, but abruptly increases above 900℃. From the above results, the optimum calcining condition for MnZn ferrites is considered to be 900℃for 2 hours.