• Proceedings of the Materials Research Society of Korea Conference
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• 2002.05a
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• pp.77-77
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• 2002

• Journal of the Korean Society for Heat Treatment
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• v.13 no.6
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• pp.412-419
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• 2000

There has been a considerable attention on Invar alloys due to its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than $10^{-6}$ near the room temperature, is attractive for electric transmission lines and precision machine tools. However, the expansion property of Invar alloys is limited below about 520K, and mechanical properties are relatively low to apply to electric transmission line. In order to improve mechanical properties in this alloy, Ti alloying element was added to the $Ni_{38}-Mo_2-Cr_1-Fe$ invar alloy. The microstructure Ti added alloy showed finer than that of the unalloyed one. It was found that the (Mo, Ti), Mo carbide formed by Ti addition obstacled grain growth by pinning effect and supplyed recrystallization sites during heat-treatment. Optimum heat-treatment conditions with Ti addition were also discussed in the modified Invar alloy.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.642-646
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• 2015

Super alloys, which can be divided into three categories, i.e. Ni-base, Co-base, and Fe-base alloys, are widely used for high temperature applications. Since superalloys contain many alloying elements and precipitates, their chemistry and processing parameters need to be carefully designed. In this study, we designed a new Ni alloy to prevent corrosion due to water vapor and gases at high temperatures. The new alloy was designed using the theoretical value of the resulting energy electronic state calculation($DV-X{\alpha}$ method). The components that were finally used were Cr, Mo, and Ti, with Ni as a base. For these alloys, elements were selected in order to compare their values with that of the average theoretical basis for an Inconel 625 alloy. Finally, two kinds of Ni alloy were designed: Ni-28Cr-4Mo-2Ti and Ni-20Cr-10Mo-1Ti.

• Transactions of Materials Processing
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• v.24 no.1
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• pp.44-51
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• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.63-71
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• 2002

One of the shortcoming of ferritic stainless steels is their limited toughness. The most important factor governing the toughness of ferritic stainless steels is hewn to be their interstitial contents. Due to the limited solubility of carbon and nitrogen in the ferrite matrix, it is difficult to avoid carbide and nitride precipitates. In the study, the role of nitrogen on the toughness of 260r-2Mo superferritic stainless steel welds has been investigated using alloys containing various nitrogen levels between 100 and 1640 ppm. Mechanical properties of weld metals have been evaluated by microhardness, Charpy impact test and notch tensile test. The alloys are mainly embrittled by the grain boundary and intragranular nitride precipitation. Grain boundary precipitates are considered to be more deleterious than intrauanular nitrides. Fracture mechanism have been elucidated through microscopic evaluation of notch tensile test

• Proceedings of the Materials Research Society of Korea Conference
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• 1995.11a
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• pp.111-112
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• 1995

• Proceedings of the Korean Magnestics Society Conference
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• 1995.05a
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• pp.52-53
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• 1995

• Transactions of Materials Processing
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• v.31 no.5
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• pp.273-280
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• 2022

Although the mechanical properties of high-entropy alloys depend on the annealing conditions, limited works were established to investigate the annealing effect on the mechanical properties of Mo-added high-entropy alloys. Therefore, in the present work, the annealing effects on the microstructural evolution and mechanical properties of Mo-added high-entropy alloy were investigated. As a result, incomplete recrystallization from the limited annealing time not only suppresses deformation-induced phase transformation during cryogenic tensile test but also induces a deformation instability that results into the ductility reduction compare with the fully recrystallized sample. This result represents adjustment of annealing time is useful to control both transformation-induce plasticity and deformation instability of high-entropy alloys, and this can be applied to control the mechanical properties of metallic alloys by combining pre-straining and subsequent annealing.

• Analytical Science and Technology
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• v.11 no.3
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• pp.189-193
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• 1998

Binary alloys, $MoRu_3$ and $MoRh_3$, have been prepared using arc melting furnace. Mo and the noble metals Ru and Rh are the constituents of metallic insoluble residues, which were found in the early days of the post-irradiation studies on uranium oxide fuels. Detailed structural informations about these alloys have not been reported on JCPDS files of ICDD (International Centre for Diffraction Data). The results of X-ray diffraction study showed that the alloy was crystallized in hexagonal close-packing, well known as ${\varepsilon}$-phase. The X-ray diffraction patterns of these alloys matched well to that of $WRh_3$ with $P6_3/mmc$ of space group. The lattice parameters, a and c, were calculated using the least squares extrapolation. It was found from X-ray photoelectron spectroscopic measurements that Mo on the surface of the alloy was oxidized to Mo(6+), which could be removed by sputtering with Ar ions for approximately 15 minutes. The changes in binding energy of Mo, Ru, and Rh on the surface of the alloy were not observed. Magnetic susceptibility measurements resulted in the typical Pauli-paramagnetic behavior in the temperature range of 2 to 300 K.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.209-216
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• 2008

Super austenitic stainless steels shows the high PRE (Pitting Resistance Equivalent) number and the good corrosion resistance. This work controlled the Co contents in Fe-31Cr-1.7Mo-27Ni-0.25N alloys to elucidate the effect of cobalt contents on the biocompatibility and corrosion resistance. Increasing Co contents, the hardness of the annealed alloys tends to be reduced. In aged alloys, cobalt decreased the increments of hardness by aging treatment. Cobalt decreased the critical pitting temperature (CPT) in 6% $FeCl_3$ + 1% HCl solution, but improved the anodic polarization behavior in Hanks' balanced salt solution and artificial saliva solution. Repassivation rate in artificial body solutions was improved by increasing cobalt contents, but didn't show the linear relationship to PRE number of the alloys. The experimental alloys showed the non-cytotoxicity because of its high corrosion resistance.