• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.170-171
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• 2012

$Fe_2O_3$, Al, Cr과 Si 분말을 고 에너지 볼 밀링해서 나노분말을 제조한 후 고주파유도 가열 활성 연소합성 장치로 1분 이내의 짧은 시간에 합성 및 소결한 $Al_2O_3+4.65(Fe_{0.43}Cr_{0.17}Al_{0.323}Si_{0.077})$, $Al_2O_3$ + 5.33 ($Fe_{0.375}Cr_{0.11}Al_{0.3}Si_{0.075}$), $Al_2O_3$ + 6.15 ($Fe_{0.325}Cr_{0.155}Al_{0.448}Si_{0.072}$), $Al_2O_3$ + 3.3 ($Fe_{0.6}Cr_{0.3}Al_{0.6}$) 소결체 시편을 $700^{\circ}C$의 온도에서 100시간 동안 공기 중에서 산화 및 $N_2-H_20-H_2S$ 혼합 가스 내에서 황화 부식을 실시하였다. 그 결과 산화 및 황화 부식 후에 ${\alpha}-Al_2O_3$가 표면에 생성되어 보호 피막으로 작용하여 우수한 내식성을 보였다.

• Journal of the Korean Magnetics Society
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• v.13 no.1
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• pp.6-14
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• 2003

The purpose of this study is to investigate the effect of chemical reaction with a bonding glass on physical and magnetic properties of Fe-Hf-N/SiO$_2$ and Fe-Hf-N/Cr/SiO$_2$ thin films. When the Fe-Hf-N/SiO$_2$ films were reacted with the bonding glass, the soft magnetic properties of them were extremely degraded. At $600^{\circ}C$, the saturation magnetization of the reacted film decreased to 1 kG, and its coercivity increased to 27 Oe, and its effective permeability decreased to 70. It was found that the degradation of soft magnetic properties of the Fe-Hf-N/SiO$_2$ films reacted with the bonding glass were attributed to the oxidation of the Fe-Hf-N layers to HfO$_2$ and Fe$_3$O$_4$. The soft magnetic properties of the Fe-Hf-N/Cr/SiO$_2$ films reacted with the bonding glass were degraded less than those of Fe-Hf-N/SiO$_2$ films. At $600^{\circ}C$, the saturation magnetization of the reacted film decreased to 13.5 kG, and its coercivity increased to 4 Oe, and its effective permeability decreased to 700. It was found that the Cr layer suppressed the oxidation of the Fe-Hf-N layers during the chemical reaction between the Fe-Hf-N layer and bonding glass.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.511-514
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• 1995

The crystallization kinetics of $Fe_{73.5}Si_{13.5}B_{9}Cu_{1}Nb_{3}$ amorphous alloy has been investigated using differential scanning calorimetry (DSC). The crystallization process had two stages, i.e. precipitation of the $\alpha$-Fe(Si) solid solution and the tetragonal borides. The isothermal transformation data of the amorphous alloy has been fitted successfully to the generalized Johnson-Mehl-Avrami equation. The mean time exponent, n, obtained is close to 2.5. The value of n=2.5 may be interpreted as being due to a diffusion-controlled transformation process with a constant nucleation rate, one likely transformation mode for the crystallization of metallic amorphous alloys. The activation energy of the overall crystallization process deduced from the time to 50% crystallization are about 81 kcal/mole. The value is of the same order as those estimated from viscous flow.

• Advanced Composite Materials
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• v.18 no.4
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• pp.351-364
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• 2009

The thermal stability and elevated temperature mechanical properties of $SiC_P$/Al-11.7Fe-1.3V-1.7Si (Al-11.7Fe-1.3V-1.7Si reinforced with SiC particulates) composites sheets prepared by spray deposition (SD) $\rightarrow$ hot pressing $\rightarrow$ rolling process were investigated. The experimental results showed that the composite possessed high ${\sigma}_b$ (elevated temperature tensile strength), for instance, ${\sigma}_b$ was 315.8 MPa, which was tested at $315^{\circ}C$, meanwhile the figure was 232.6 MPa tested at $400^{\circ}C$, and the elongations were 2.5% and 1.4%, respectively. Furthermore, the composite sheets exhibited excellent thermal stability: the hardness showed no significant decline after annealing at $550^{\circ}C$ for 200 h or at $600^{\circ}C$ for 10 h. The good elevated temperature mechanical properties and excellent thermal stability should mainly be attributed to the formation of spherical ${\alpha}-Al_{12}(Fe,\;V)_3Si$ dispersed phase particulates in the aluminum matrix. Furthermore, the addition of SiC particles into the alloy is another important factor, which the following properties are responsible for. The resultant Si of the reaction between Al matrix and SiC particles diffused into Al matrix can stabilize ${\alpha}-Al_{12}(Fe,\;V)_3Si$ dispersed phase; in addition, the interface (Si layer) improved the wettability of Al/$SiC_P$, hence, elevated the bonding between them. Furthermore, the fine $Al_4C_3$ phase also strengthened the matrix as a dispersion-strengthened phase. Meanwhile, load is transferred from Al matrix to SiC particles, which increased the cooling rate of the melt droplets and improved the solution strengthening and dispersion strengthening.

• Korean Journal of Materials Research
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• v.11 no.12
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• pp.1068-1073
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• 2001

An n-type iron$silicide(Fe_{0.98}Co_{0.02}Si_2)$has been produced by mechanical alloying process and consolidated by vacuum hot pressing. Although as-milled powders after 120 hours of milling did not show an alloying progress,${\beta}-FeSi_2$phase transformation was induced by isothermal annealing at$830{\circ}C$for 1 hour, and the fully transformed${\beta}-FeSi_2$phase was obtained after 4 hours of annealing. Near fully dense specimen was obtained after vacuum hot pressing at$ 1100{\circ}C$with a stress of 60MPa. However, as-consolidated iron silicides were consisted of untransformed mixture of ${\Alpha}-Fe_2Si_5$and ${\varepsilon-FeSi$phases. Thus, isothermal annealing has been carried out to induce the transformation to a thermoelectric semiconducting${\beta}-FeSi_2$phase. The condition for${\beta}-FeSi_2$transformation was investigated by utilizing DTA, SEM, and XRD analysis. The phase transformation was shown to be taken place by a vacuum isothermal annealing at$830{\circ}C$and the transformation behaviour was investigated as a function of annealing time. The mechanical properties of${\beta}-FeSi_2$materials before and after isothermal annealing were characterized in this study.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.2
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• pp.61-67
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• 2019

This study was carried out to investigate the effect of thermo-mechanical treatment on the tensile properties of Fe-20Mn-12Cr-3Ni-3Si alloy with deformation induced martensite transformation. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite, dislocation, stacking fault were formed, and grain size was refined by thermo-mechanical treatment. With the increasing cycle number of thermo-mechanical treatment, volume fraction of ${\varepsilon}$ and ${\alpha}^{\prime}$-martensite, dislocation, stacking fault were increased, and grain size decreased. In 5-cycle number thermo-mechanical treated specimens, more than 10% of the volume fraction of ${\varepsilon}$-martensite and less than 3% of the volume fraction of ${\alpha}^{\prime}$-martensite were attained. Tensile strength was increased and elongation was decreased with the increasing cycle number of thermo-mechanical treatment. Tensile properties of thermo-mechanical treated alloy with deformation induced martensite transformation was affected to formation of martensite by thermo-mechanical treatment, but was large affected to increasing of dislocation and grain refining.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.3
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• pp.160-166
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• 2001

The change of ribbon geometry, microstructure and shape recovery with Mn contents, wheel speed and various annealing temperature have been studied in Fe-X%Mn-5Cr-5Co-4Si (X%=15, 20, 24) shape memory alloy (SMA) ribbons rapidly solidfied by single roll chill-block melt-spinning process. The thickness and width of melt-spun ribbons are reduced, results in refining and uniformalizing grains with increasing wheel speed. In the ribbons melt-spun at a wheel speed of 15m/sec, both ${\varepsilon}$ and ${\alpha}^{\prime}$martensites are formed in ribbon 1 (15.5wt%Mn), while only ${\varepsilon}$ martensite is revealed in ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn). The volume fraction of ${\varepsilon}$ martensite is decreased with increasing Mn contents, and those of ${\varepsilon}$ as well ${\alpha}^{\prime}$martensites are increased due to thermal stress relief and grain growth with increasing annealing temperature. Ms temperatures of the ribbons 1, 2 and 3 are fallen with increasing Mn contents. $M_s$ temperatures of the ribbons 1, 2 and 3 annealed at $300^{\circ}C$ for 3 min are risen abruptly, but are nearly constant even at higher annealing temperature, i.e., 400, 500 and $600^{\circ}C$ for 3 min. Shape recovery of the ribbons 1, 2 and 3 increased 30%, 52% and 69% with Mn contents, respectively. Shape recovery of ribbon 1 (15.5wt%Mn) formed ${\varepsilon}$ and ${\alpha}^{\prime}$martensites decreased because of the presence of ${\alpha}^{\prime}$martensite but those of ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn) formed ${\varepsilon}$ martensite increased with increasing annealing temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.411-414
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• 2005

It is reported that $\varepsilon$ (HCP) and $\gamma$ (FCC) phases of a Fe-17Mn alloy transform to $\alpha'$ phase, which has BCC structure, under a deformation condition. In this study, we investigated the effect of strain-induced-transformed $\alpha'$ phase on sliding wear of the Fe-17Mn alloy that originally had e and y phases. Wear tests of the materials were carried out using a pin-on-disk wear tester at various loads of 0.5N-50N under a constant sliding speed condition of 0.38m/s against glass $(83\%\;SiO_2)$ beads. The sliding distance and radius were loom and 9 mm, respectively. Wear rate of the Fe-17Mn alloy was calculated by dividing the weight loss, measured to the accuracy of $10^{-5}g$ by the measured specific gravity and sliding distance. Worn surface and wear debris of the specimens were examined using an SEM and XRD. During the wear, $\alpha'$ phase of BCC structure was formed by strain-induced transformation when the applied wear load exceeded critical values. The $\alpha'$ phase formed by the strain induced transformation increased the wear rate of the Fe-17Mn alloy.

• Journal of the Korean Magnetics Society
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• v.20 no.3
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• pp.114-119
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• 2010

Fe compounds of volcanic rock samples distributed in the seaside area of Ulleung island were investigated by means of X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF) and M$\ddot{o}$ssbauer spectroscopy. We found that samples were typical basic rock which had the total amount of iron compounds including hematite ($\alpha-Fe_2O_3$) varies from 10.6 w% to 14.5 w% depending on the different regions by XRF. The M$\ddot{o}$ssbauer spectra of the samples were consisted of one sextet due to hemitite and doublets due to $Fe^{3+}$ in various clay mineral and $Fe^{2+}$ in pyroxene $(Ca,Fe,Mg)_2(SiO_4)_2$, ilmenite ($FeTiO_3$) and olivine $(Mg,Fe)_2SiO_4$. The balance state of Fe ions of all samples was chiefly $Fe^{3+}$, so we could find that the volcanic rocks distributed in the seaside area of Ulleung island were made in inland.

• Journal of the Korean Ceramic Society
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• v.29 no.7
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• pp.511-516
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• 1992

In this study, SiC powder and Si powder were used as the raw materials. Mixture was prepared with addition of Al2O3 and Fe2O3 at 0.1~0.5wt% respectively. After this step, the mixture was pressed and nitrided for 30 hrs at 140$0^{\circ}C$ under NH3-N2 atmosphere. Mechanical properties of sintered specimens were investigated from measurement of porosity, bulk density and three point bending test. nitration reaction extent was observed at the change of mass before and after reaction, and the microstructure and the change of $\alpha$-Si3N4 and $\beta$-Si3N4 were observed by XRD and SEM. In the current work, the results are as follows 1. When Fe2O3 added, the nitridation increased with the content of Fe2O3, and the bending strength was increased from 0.1 wt% to 0.3 wt%, and decreased to 0.5 wt%. 2. When Al2O3 added, the nitridation and the bending strength increased little by little with the content of Al2O3 3. The bending strength of the specimen added with Fe2O3 were higher than that with Al2O3. Because the specimens contained Fe2O3 had much more the whisker type crystal of Si3N4 contributing to strength than contained Al2O3.