• Journal of Power System Engineering
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• v.13 no.3
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• pp.47-52
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• 2009

The effect of forging start temperature, forging ratio on the microstructure and mechanical properties of B7B4 steel ware investigated. Microstructure of centrifugal casted B7B4 steel consisted of martensite and ferrite phase. The volume fraction of ferrite increased with increase of forging start temperature and decreased with increase of forging ratio. Tensile strength and hardness decreased with higher of forging start temperature, while impact value and elongation increased with higher of forging start temperature. With increase of forging ratio, tensile strength rapidly increased up to the forging ratio of 30%, and then slowly increased, but elongation was decreased. Hardness and impact value rapidly increased with increase of forging ratio.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.178-181
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• 2005

Quaternary Ti-Si-C-N coatings were deposited on WC-Co substrates by a hybrid coating system of arc ion plating (AIP) and sputtering techniques using Ti and Si targets, in an $Ar/N_2/CH_4$ gaseous mixture. The crystallinity, bending status, and microstructure of the Ti-Si-C-N coatings were measured by X-ray diffractometer (XRD) and X-ray photoelectron spectroscope (XPS), The micro-hardness of Ti(C,N) and Ti-Si-N coatings were about 30 and 40 GPa, respectively. As the Si was incorporated into Ti(C,N) coatings, the Ti-Si-C-N coatings having Si content of $8.9\;at.\%$ showed the maximum hardness value of about 55 GPa. In this work, the microstructure and mechanical properties of Ti-Si-C-N coatings were systematically investigated.

• Transactions of Materials Processing
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• v.8 no.5
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• pp.437-448
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• 1999

The reheating of the billet in the semi-solid state as quickly and homogeneously as possible is one of the most imposrtant parts. To obtain a fine globular microstructure in cross section of billet, the optimal design of the induction coil for variation of alloys and specimen sizes is necessary. For the thixo-forging process the construction of the reheating data base is very important, because the reheating conditions are different for variation of SSM and billet sizes. So in this study, the optimal coil design of A356 (ALTHIX) and Aι2024 with d×ι=60×90 (mm) to obtain the globular microstructure is theoretically proposed. The suitability of an optimal coil design will be demonstrated by reheating experiments. Finally, the thixoformability of an arbitrarily shaped product is evaluated by its forming variables. The defects and mechanical properties are also investigated.

• Transactions of Materials Processing
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• v.18 no.6
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• pp.458-464
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• 2009

Thermal energy control is a important factor to control properties of large sized product in ingot-forging. Good control of thermal energy helps to increase characteristics and eliminate defects of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment process by FEM simulation. Changes of temperature and microstructure for forged shell were predicted according to different heat treatment conditions. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.

• Korean Journal of Materials Research
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• v.16 no.1
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• pp.5-10
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• 2006

This study was performed to investigate the characteristics of the synthesized powder type ferro materials for wear resistant hardfacing. The powder type filler materials were made from ferro Cr and ferro Mn. Those ferro materials are two types, such as high carbon and low carbon contained. The alloy composed of high carbon ferro Cr and high carbon ferro Mn exhibited the best properties in terms of microstructure and hardeness for wear characteristics. Further, the alloys produced by the synthesized powders and wire type filler, were also evaluated in terms of microstructures and microhardness measurements. The results indicated that the synthesized powders displayed reasonable properties compared to commercial grade materials. The hardness value of the alloy produced by the synthesized powders were approached about 90% of the commercial grade's hardness. The hardness values of the alloys closely depended on the amount of the dissolution of the ferro Cr, the hardness and the volume of the eutectic phase.

• Journal of Surface Science and Engineering
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• v.46 no.2
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• pp.55-60
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• 2013

Superhard TiN coatings were fabricated by DC and ICP (inductively coupled plasma) assisted magnetron sputtering techniques. The effect of ICP power, ranging from 0 to 300 W, on coating microstructure, preferred orientation mechanical properties were systematically investigated with HR-XRD, SEM, AFM and nanoindentation. The results show that ICP power has a significant influence on coating microstructure and mechanical properties of TiN coatings. With the increasing of ICP power, coating microstructure evolves from the columnar structure of DC process to a highly dense one. Grain sizes of TiN coatings were decreased from 12.6 nm to 8.7 nm with increase of ICP power. The maximum nanohardness of 67.6 GPa was obtained for the coatings deposited at ICP power of 300 W. Preferred orientation in TiN coatings also vary with ICP power, exerting an effective influence on film nanohardness.

• Journal of Surface Science and Engineering
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• v.32 no.2
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• pp.100-108
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• 1999

The microstructure and corrosion properties of Al-Si diffusion coated PWA1426 alloy have been investigated. Experimental variables are included temperatures of heat-treatment and coating thickness. The microstructure of coated layer and corrosion properties were analysed by SEM, EDS and hot corrosion test. Two major processes have been found to contribute to microstructural changes in the coating. These are, firstly, the transformation of the NiAl to other $Ni_2Al_3$-based phase and secondly, the precipitation of Cr containing phases. Specimens heat treated at $1080^{\circ}C$ showed superior corrosion resistance to heat treated at $880^{\circ}C$. These increase in life was attributed to the transformation of NiAl and increased coating thickness of PWA1426 alloy.

• Journal of Korea Foundry Society
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• v.28 no.2
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• pp.69-73
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• 2008

In the present study, microstructural evolution and mechanical properties of Ti-Fe-Sn ultrafine eutectic alloys have been investigated. Ultrafine eutectic microstructure consisting of a mixture of ${\beta}$-Ti solid solution and TiFe intermetallic compound homogeneously formed in $(Ti_{70.5}Fe_{29.5})_{100-x}Sn_x$ alloys with x = 0, 1 and 3. Addition of Sn is effective to modify the eutectic colony into the spherical shape with decreasing the lamellar spacing and colony size. This results in enhancing the macroscopic plasticity up to 3.1% of the Ti-Fe-Sn ultrafine eutectic alloys.

• Journal of the Korean Ceramic Society
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• v.31 no.3
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• pp.235-240
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• 1994

The electric and magnetic properties of Mg1.9-2xMn0.05Fe4xO4+${\gamma}$+2wt% Al2O3, and its microstructure have been investigated as a function of ferrite composition (x=0.45, 0.5, 0.55). The microstructure turned out to be independent on the ferrite composition. The resistivity was decreased with increasing Fe contents, whereas the Curie temperature decreased. Saturation magnetization was varied from 1741 to 2022 G with composition, and squareness ratio (SR), coercive force (BHc) were decreased and increased with increasing Fe contents respectively, so the sample which SR and BHc were 0.97 Oe and 1.49 Oe can be attainable at x=0.45.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.824-825
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• 2006

Homogeneous microstructures of the PM compacts are difficult to attain when mixed elemental powders are used. This study examined the microstructures of pressed-and-sintered and MIM products that contain Ni and Mo.Ni-rich areas, which were lean in carbon and were soft and were found easily in regular specimens. Gaps or cracks near the Ni-rich or Mo-rich areas were also frequently observed. This problem worsened when Ni and Mo particles were large and were irregular in shape. By using ball milling treatment and ferroalloy powders, the microstructure homogeneity and mechanical properties were improved. The addition of 0.5wt%Cr further improved the distribution of Ni because Cr reduced the repulsion effect between nickel and carbon. With the elimination of Ni-rich areas, more bainites and martensites were formed and mechanical properties were significantly improved.