• Journal of Power System Engineering
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• v.9 no.1
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• pp.76-81
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• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.2
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• pp.112-120
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• 1996

The effects of ${\varepsilon}$ martensite content and strain amplitude on damping capacity of an Fe-17%Mn alloy have been studied to establish damping mechanism of Fe-Mn system corresponding to the magnitude of strain amplitude. In a range of $1{\times}10^{-4}{\sim}3{\times}10^{-4}$ strain amplitude, the damping capacity is linearly proportional to the ${\varepsilon}$ martensite content, which suggests that stacking faults and ${\varepsilon}$ martensite variant boundaries are the principal damping sources. In the range of $4{\times}10^{-4}{\sim}6{\times}10^{-4}$ strain amplitude, however, a maximum damping capacity is observed around 68 vol.% ${\varepsilon}$. This behavior is very similar to dependence of relative area of ${\gamma}/{\varepsilon}$ interface on ${\varepsilon}$ martensite content. This means that in this strain range, ${\gamma}/{\varepsilon}$ interface acts as damping source in addition to the stacking faults and variant boundaries in Fe-17%Mn alloy.

• Journal of the Korean Magnetics Society
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• v.12 no.4
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• pp.132-136
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• 2002

Enhancement of crystallinity and exchange bias characteristics for NiFe/FeMn/NiFe trilayer with Si buffer layer fabricated by ion-beam deposition were examined. A Si buffer layer promoted (111) texture of fcc crystallities in the initial growth region of NiFe layer deposited on it. FeMn layers deposited on Si/NiFe bilayer exhibited excellent (111) crystal texture. The antiferromagnetic FeMn layer between top and bottom NiFe films with the buffer Si 50 ${\AA}$-thick induced a large exchange coupling field Hex with a different dependence. It was found that H$\sub$ex/ of the bottom and top NiFe films with Si buffer layer revealed large value of about 110 Oe and 300 Oe, respectively. In the comparison of two Ta and Si buffer layers, the NiFe/FeMn/NiFe trilayer with Si could possess larger exchange coupling field and higher crystallinity.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1555-1557
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• 1998

In order to investigate the core material for over-head transmission line with non-magnetic and high strength nitrogen steel, microstructure and several basic properties of Fe-Mn-Cr-Ni-N steel have been studied. It is necessary that core material have a $\gamma$ phase to have a non-magnetic characteristics. To acquire a $\gamma$ phase, Mn, Ni and C are added as a alloying element. It was found that Fe-25Mn-16Cr-1Ni-N alloy have a stable $\gamma$ phase. The precipitate from this alloy system was $(Cr, Fe)_7C_3$. High Mn and N steel satisfies Sievert's relation that solubility of nitrogen increases with the square root of partial pressure of gas in metal-gas system and the hardness have proportional relation with nitrogen concentration.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.2
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• pp.99-104
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• 2005

In this study, the effects of C and Si on damping capacity and mechanical properties of as-cast and as-rolled Fe-17%Mn alloys were investigated as a basic study for the purpose of the commercialization of the alloy. The $M_s$ temperature of ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation in Fe-17%Mn alloy was decreased with increasing C and Si contents, resulting in the less volume fraction of ${\varepsilon}$ martensite. The damping capacity was also decreased with increasing alloying content because of less ${\varepsilon}$ amount and the reduction in mobility of the damping sources such as the stacking fault boundaries and ${\gamma}/{\varepsilon}$ interfaces due to the pinning effect by alloying elements. The mechanical properties of as-rolled alloys were superior to those of as-cast alloys probably because of finer ${\gamma}$ grains, larger amount of ${\varepsilon}$ martensite, and chemical homogeneity.

• Korean Journal of Materials Research
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• v.5 no.1
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• pp.22-35
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• 1995

In this study, crystal structures and magnetic properties of as-ast, annealed and rapidly solidified Mn-A1-M( M=Cu, Fe) alloys have been investigated. In $Mn_{0.56}Al_{0.44}$ alloys, the largest fraction of $\tau$ phase and values of magnetic properties was obtained in Mnl, i6Alo or alloy. And this alloy was used as the basic composition. In $Mn_{0.56-X}M_{X}Al_{0.44}$ alloys, when annealed, $\tau$- and $\beta$-Mn phase appeared at x< 0.08, $\tau$- and $\kappa$ phase at 0.10 $\leq x \leq$ 0.12 and $\kappa$- phase only at 0.15 $\leq x \leq$0.20 . When rapidly solidified, specimens showed similar phases as when annealed except that $\varepsilon$ phase appeared at x=0.04. In Mnu FexAlo 44 alloys, asyast specimens showed $\tau$-, $\beta$-Mn and $\gamma_2$- phase at x<0.08 and K and $\beta$-Mn phase at x>0.10. When rapidly solidified, Mn-Fe-Al specimens showed $\varepsilon$-, $\gamma_2$- and small amount of $\tau$- and $\kappa$ phase at x<0.08 and $\kappa$- phase only at 0.$\leq x \leq$0.20. All the alloys investigated were ferromagnetic. The Curie temperature of annealed specimens and rapidly solidified of Mno 5sAlu 44 alloy were -650K and -644K. Spontaneous magnetization( UII of annealed and rapidly solidified specimens were 40-45 (emu/g) and 50-52(emu/g), respectively. Remanent (M,) to saturation magnetization( Ms) ratio was -0.7. M, of rapidly solidified specimen was about 48(emu/g). Magnetic properties of $Mn_{0.56}Al_{0.44}$ alloys were found to be determined by the relative fraction of ferromagnetic r- and K- phase. When M= Cu and x=0.15, maximum as($\sigma_{0.0}$) was obtained by about 64.3 emu/g), and when M=Fe and x=0.15, 66.4( emu/g). The Curie temperature decreased as x increased.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.266-278
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• 1995

The high strain-rate dynamic plastic behavior of Fe-X%Mn alloys was investigated. The strain rate did not have an effect when tested under quasi-static strain rates($2{\times}10^{-3}/sec$ and $2{\times}10^{-1}/sec$). However, the true stress increased at all strain levels when the strain rate increased to $6{\times}10^3/sec$. Based on the experimental results, an constitution equation to calculate the dynamic strength for strain rates over $10^4/sec$ was determined. The Fe-5%Mn alloy containing athermal ${\alpha}^{\prime}$ martensite initially did not show work hardening. The work hardening increased with Mn content showing a maximum at 20% Mn. The high work hardening of Fe-20%Mn and Fe-30%Mn alloys appears to be closely related not only to the initial amounts of ${\varepsilon}$ martensite but to the strain induced transformation (${\gamma}{\rightarrow}{\varepsilon}$ and ${\varepsilon}{\rightarrow}{\alpha}^{\prime}$) occurring during each stages of deformation.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.3
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• pp.197-204
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• 1995

In recent work, we reported that a hot-rolled Fe-18wt%Mn alloy exhibited high damping capacity as well as excellent mechanical properties. It was also proposed that damping capacity of the alloy was proportional to the ${\gamma}/{\varepsilon}$ boundary area. In the present study, the effects of homogenization(12hrs at $1100^{\circ}C$) and solution treatment(1hr at $1050^{\circ}C$ before air cooling) on damping capacity and mechanical properties were investigated for as-cast and heat treated Fe-18wt%Mn alloy. The specimen subjected to both homogenization and solution treatment was found to show superior damping capacity and mechanical properties to the as-cast state due to removal of segregation and increase in ${\gamma}/{\varepsilon}$ boundary area.

• Journal of the Korean Magnetics Society
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• v.3 no.1
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• pp.7-12
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• 1993

The effects of Mn, Cr or Co addItion on the magnetic properties of Fe-Ni Invar alloys were investigated. The composition range of the three additives is up to 5wt%. In the temperature range of room temperature-$250^{\circ}C$, the variation of specific magnetization with the addition of Mn, Cr or Co in the Fe-Ni alloys except for 5wt% Co shows the phenomenon characteristics of the Invar effect, viz., the specific magnetization decreases very abrubtly with the temperature and the dependence of temperature on the specific magnetization is in the mixed form of $T^{3/2}$ and $T^{2}$. In the room temperature, the amount of increase in the specific magnetization, Curie temperature and coercivity is in order of Co > Cr > Mn. In the case of 5wt% Co an anomalous phenomena were observed due to the occurrance of ferromagnetic $\alpha$ phase which reduces the invar effect.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.3
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• pp.158-162
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• 2000

The high temperature oxidation behavior and the surface defect in Fe-25Mn-1.5A1-0.5C steel was investigated by XRD (X-ray Diffractin) and electron microscopy. The intra- and inter-granular oxides were formed by the selective oxidation of manganese and aluminum, which were identified to MnAl2O4 phase. Aluminum nitride (AlN) was formed in front of these oxides. The ${\gamma}$-matrix was transformed to ${\alpha}$- and ${\varepsilon}$- phases by the selective oxidation of manganese. The surface defect, micro-scab was induced by the difference of the high temperature ductility between the matrix and the inter-granular oxide.