• Title/Summary/Keyword: iron alloy

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Effect of Transformation Cycles(α' ↔ γ')on Microstructures and Mechanical Properties of Lath and Lenticular Martensites in Fe-Ni Alloys (Fe-Ni 합금에서 래쓰 마르텐사이트와 렌즈상 마르텐사이트의 반복변태사이클(α' ↔ γ')에 따른 미세조직과 기계적 성질)

  • Seo, Seong-Bok;Jun, Joong-Hwan;Choi, Chong-Sool
    • Journal of the Korean Society for Heat Treatment
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    • v.13 no.2
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    • pp.85-90
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    • 2000
  • The influence of transformation cycles (${\alpha}^{\prime}{\leftrightarrow}{\gamma}^{\prime}$) on the microstructure and mechanical properties of lath and lenticular martensites has been studied in Fe-Ni alloys. The width of lath in Fe-15%Ni alloy decreased with increasing the number of transformation cycles, while no appreciable change in dislocation density inside the lath was observed. In case of Fe-31%Ni alloy, a number of dislocations were additionally introduced into the martensite plate after the transformation cycling. Tensile strength and Vickers hardness of lath martensite decreased with the increase in number of transformation cycles, whereas those of lenticular martensite increased up to 1 cycle and then remained constant. Elongation of two alloys was deteriorated after 1 transformation cycling, corresponding to the tensile strength. But the decrement of elongation in Fe-31%Ni alloy was smaller than that in Fe-15%Ni alloy.

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Toward high-performance iron based alloys: Ab initio study

  • Kang, S.J.;Kim, Mi-Young;Kwon, Young-Kyun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.53-53
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    • 2010
  • Car industry has required light-weight steels, but still with strong mechanical strength. To meet this requirement, a variety of researches on Fe-Al alloys have been performed. As Al is being added in a disordered manner, alloys become more ductile and show higher yield stress. At a certain concentration of Al, however, the Fe-Al alloy system falls in a second phase whose mechanical strength is worsened. To understand the microscopic role of Al, we investigate the stability and the elastic properties of various Fe-Al alloys using ab initio density functional theory. At agiven Al concentration, the equilibrium geometry is obtained among several disordered Fe-Al alloy structures by performing the geometry relaxation. The formation energies and elastic properties such as bulk moduli of the equilibrium structures are also computed as a function of Al concentration. We also investigate the effects of different elements such as Si and Mn. Fe-Si alloy systems exhibit unusual mechanical behaviors requiring further investigation to understand their physical origin. Especially, the microscopic role of Mn is investigated to find its physical origin of preventing the Fe-Al alloy system from forming an unfavorable second phase. The effect of manganese on mechanical properties of Fe-based alloys is also explored.

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Study on the Distillation of Magnesium Alloy Scrap (마그네슘 합금 스크랩의 진공증류에 관한 연구)

  • Wi, Chang-Hyun;Yoo, Jung-Min;Jang, Byoung-Lok;You, Byoung-Don
    • Korean Journal of Metals and Materials
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    • v.46 no.1
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    • pp.13-19
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    • 2008
  • To develop a recycling process of magnesium alloy scrap, a fundamental study on the distillation of magnesium alloy melt was carried out. Melt temperature, vacuum degree and reaction time were considered as experimental variables. The amount of vaporized magnesium melt per unit surface area of melt increases with the increase of melt temperature, reaction time and vacuum degree. The vapor condensed at the tip of water cooling Cu-condenser as a form of pine cone. Magnesium and zinc were vaporized easily from the melt. However, It's difficult to separate magnesium and zinc by vacuum distillation because vapor pressure of zinc is similar to one of magnesium. The contents of aluminum, manganese and iron, etc. in residual melt increase due to the decrease of magnesium and zinc content after the distillation of magnesium alloy.

The Effect of Annealing Heat Treatment by Anodic Polarization Impedance Experiments for Cu-10%Ni Alloy

  • Lee, Sung-Yul;Moon, Kyung-Man;Jeong, Jae-Hyun;Lee, Myeong-Hoon;Baek, Tae-Sil
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.5
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    • pp.536-541
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    • 2015
  • Copper has been used extensively as an electric wire or as a base material in various types of machineries owing to its good electrical and thermal conductivity and good fabricating property, as well as its good corrosion resistance compared to iron. Furthermore, the copper-nickel alloy has significant corrosion resistance in severely corrosive environments. Although, cupro-nickel alloy shows better corrosion resistance than the brass and bronze series, this alloy also corroded in severely corrosive environments, including aggressive chloride ions, dissolved oxygen, and condition of fast flowing seawater. In this study, and annealing treatment at various annealing temperatures was carried out on the cupro-nickel (Cu-10%Ni) alloy, and the effects of annealing were investigated using electrochemical methods, such as measuring the polarization and impedance behaviors under flowing seawater conditions. The corrosion resistance increased by annealing compared to non heat treatment in the absence of flowing seawater. In particular, the sample annealed at $200^{\circ}C$ exhibited the best corrosion resistance. The impedance in the presence of flowing seawater showed higher values than in the absence of flowing seawater. Furthermore, the highest impedances was observed in the sample annealed at $800^{\circ}C$, irrespective of the present of flowing seawater. Consequently, the corrosion resistance of cupro-nickel (Cu-10%Ni) alloy in a severely corrosive environment can be improved somewhat by annealing.

Synthesis and Magnetic Properties of Body-centered-tetragonal Fe-Co Alloy (체심정방정 구조 Fe-Co계 합금상의 합성 및 그 자기적 특성)

  • Kim, K.M.;Kwon, H.W.;Lee, J.G.;Yu, J.H.
    • Journal of the Korean Magnetics Society
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    • v.27 no.4
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    • pp.129-134
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    • 2017
  • Bulk-type body-centered-tetragonal Fe-Co alloy was synthesised by utilising a conventional alloy preparation technologies, such as melting, solidification, and homogenising treatments, and its magnetic properties were investigated. In the $(Fe_{100-x}Co_x)_{1-y}C_y$ alloy, the composition range, from which single phase body-centered-tetragonal alloy (martensite phase) was obtained, was severely limited: Co content x = 2.5, and C content y = 0.062. Tetragonality(c/a) of the synthesised body-centered-tetragonal $(Fe_{97.5}Co_{2.5})_{0.938}C_{0.062}$ alloy was 1.05. Magnetocrystalline anisotropy constant ($K_1$) of the body-centered-tetragonal $(Fe_{97.5}Co_{2.5})_{0.938}C_{0.062}$ alloy was measured to be $9.8{\times}10^5J/m^3$), which was 3.1 time as high as the pure iron (${\alpha}-Fe$).

Study of the Distillation of Ferromanganese Alloy Melts at Reduced Pressure (훼로 망간 합금철 용탕의 감압 증류에 관한 연구)

  • Hong, Seong-Hun;Jeon, Byoung-Hyuk;You, Byung-Don;Kim, Jong-Deok;Jang, Pill-Yong;Kang, Soo-Chang;Geum, Chang-Hun
    • Korean Journal of Metals and Materials
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    • v.48 no.2
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    • pp.154-162
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    • 2010
  • A fundamental study of the distillation behavior of ferromanganese alloy melts was carried out at 1773 K and 0.1333 kPa (=1 Torr). During the distillation of ferromanganese alloy melts under reduced pressure, manganese vaporizes preferentially to phosphorus and other solute elements. High purity manganese metal with a very low content of solute elements can be obtained by distillation of ferromanganese alloy melts. The evaporation of manganese is suppressed as the carbon content of ferromanganese alloy melt increases due to the decrease of activity and vapor pressure of the manganese. When the carbon content of ferromanganese alloy melt is high, melt droplets are ejected from the bath, especially in the early stages of the distillation, and the solute elements in the splashed droplets contaminate the condensed material. The ejection of melt droplets is presumed to be caused by the increase of melting temperature and viscosity of the surface layer of melt due to the enrichment of solute elements such as carbon and iron.

The Behavior of Pitting Corrosion Associated with Microstructure of a Cast Lean Duplex Stainless Steel in Chloride Environments (염화물 환경에서 린 듀플렉스 스테인리스 주강의 미세조직과 연계한 공식 거동)

  • In-Sung Lee;Soon-Tae Kim;Chae-Jin Nam;Seung-Man Yang;In-Sung Cho;Seung-Mok Yoo
    • Journal of Korea Foundry Society
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    • v.43 no.5
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    • pp.230-240
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    • 2023
  • The pitting corrosion behavior of 329LD cast lean duplex stainless steel and CF3M cast austenitic stainless steel was investigated in chloride environments. The pitting corrosion resistance of the 329LD alloy was superior to that of the CF3M alloy because the pitting potential, passive region, and critical pitting temperature of the low Ni-low Mo 329LD alloy were higher than those of the high Ni-medium Mo commercial CF3M alloy. There are two main reasons for the enhancement of the pitting corrosion resistance of high Cr-low Momedium N 329LD alloy compared to the low Cr-medium Mo CF3M alloy: First, the pitting resistance equivalent number (PRENδ+γ) value of the 329LD alloy is higher than that of the CF3M alloy. Second, the passive region of the 329LD alloy is larger than that of the CF3M alloy. It indicates that the synergistic effect of the three elements by adding high Cr and low Mo-medium N to the 329LD alloy enhances the passivity of the passive film, thereby increasing the pitting corrosion resistance. It was verified that based on the PRENγ of austenite (γ) and PRENδ of ferrite (δ) values calculated using an N-factor of 16, the pitting corrosion of the 329LD alloy was selectively initiated at the γ-phases because PRENγ value of austenite (γ) was smaller than that of ferrite (δ), and finally propagated from the γ-phase to the δ-phase.

Advanced Metallic Coating for the Improvement of Corrosion and Erosion Resistance of Iron Base Materials Used in Buildings and Special Works

  • Jayaraj, J.;Seok, H.K.;Byun, K.H.;Fleury, E.;Hong, K.T.
    • Corrosion Science and Technology
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    • v.4 no.2
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    • pp.64-68
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    • 2005
  • Various metallic materials are coated on Fe base materials via thermal spraying or welding process to improve both corrosion resistance as well as erosion resistance of the Fe base materials used in buildings and special works. The mechanical properties and corrosion resistance of the coat are estimated by means of hardness measurement and anodic polarization test. In additions, the effect of alloying elements and microstructure of the coatings on the mechanical and chemical properties of the coat is investigated using X- ray diffraction, Optical microscope, Transmission electron microscopy and Auger analysis. The coating deposited by tungsten inert gas (TIG) welding exhibit a good combination of hardness and corrosion properties.

THREE-BODY ABRASIVE WEAR IN A BALL-CRATERING TEST WITH LARGE ABRASIVE PARTICLES

  • Stachowiak, G.B.;Stachowiak, G.W.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.199-200
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    • 2002
  • Three-body abrasive wear resistance of mild steel, low alloy steel (Bisalloy) and 27%Cr white cast iron was investigated using a ball-cratering test. Glass beads, silica sand, quartz and alumina abrasive particles with sizes larger than $100{\mu}m$ were used to make slurries. It was found that the wear rates of all three materials tested increased with time when angular abrasive particles were used and were rather constant when round particles were used. This increase in wear rates was mainly due to the gradual increase in ball surface roughness with testing time. Abrasive particles with higher angularity caused higher ball surface roughness. Mild steel and Bisalloy were more affected by this ball surface roughness changes than the hard white cast iron. Generally, three-body rolling wear dominated. The contribution of two-body grooving wear increased when the ball roughness was significant. More grooves were found when round particles were used or the size of the particles was decreased.

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Sliding Wear Properties of Borided Iron and Steel in Fluidized Bed Furnace (유동상열처리로에 의해 BORIDING처리한 철강재료의 미끄럼마모특성연구)

  • Lee, Han-Young;Bae, Seok-Choun
    • Journal of the Korean Society for Heat Treatment
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    • v.9 no.4
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    • pp.261-270
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    • 1996
  • Boriding is one of the chemical methods to achieve the case hardening of steel as well as nitriding or carburizing. The surface layer of the borided steel shows higher hardness and exhibits better resistance to corrosion or fatigue than the nitrided or carburized steel. The great majority of previous studies were confined to mild steel or some alloy steel. To enlarge the application, ductile cast iron (DCI) as a material for boriding has been tried in this study. Thus, sliding wear test has conducted using a pin-on-disc machine to compare between borided DCI and mild steel in fluidized bed furnace. The results show that the wear resistance of borided DCI is improved. Especially it is more efficient in the case of occurence of the mechanical wear.

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