Journal of Powder Materials

New Trend of Farication Technology for Sintered Machine Part: Dong-Kyu Park, Yong-Jin Kim; J Korean Powder Metall Inst. 2006;13(1):1-9.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.001

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Plastic Deformation Behavior of Sintered Fe-Based Alloys for Light-Weight Automotive Components
Yohan Kang, Suchul Yoon, Minwook Kim, Seok-Jae Lee
Applied Science and Convergence Technology.2014; 23(3): 151. CrossRef
Preparation and gas sensitivity of SnO2 nanopowder homogenously doped with Pt nanoparticles
Young-In Lee, Kun-Jae Lee, Don-Hee Lee, Young-Keun Jeong, Hee Soo Lee, Yong-Ho Choa
Current Applied Physics.2009; 9(1): S79. CrossRef

Formation of a Core/Rim Structure in Ti(C, N)-based Cermets: Suk-Hwan Kim; J Korean Powder Metall Inst. 2006;13(1):10-17.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.010

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Abstract PDF: Model experiment was introduced to obtain the formation of a core/rim structure by only liquid phase reaction in Ti(C, N)-based cermet alloys. Infiltrated Ti(C, N)-Ni, MO_2C-Ni, and TaC-Ni cermets were bonded to sandwiched specimen by heat treatment 1450°C for 5hr. With nitrogen addition, both (Ti, Mo) (C, N) and (Ti, Ta) (C, N) rim structure was nucleated around comer of cuboidal Ti(C, N) core. However, equilibrium shapes of(Ti, Mo) (C, N) and (Ti, Ta) (C, N) rim were different possibly due to the effect of interface energy. The core/rim and rim! binder interfaces were parallel to each other with TaC addition, while rotated to each other with MO_2C addition.

Brazing Adhesion Properties of Ag Coated W-Ag Electric Contact on the Cu Substrate: Hyun-Goo Kang, Yun-Sung Kang, Jai-Sung Lee; J Korean Powder Metall Inst. 2006;13(1):18-24.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.018

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Abstract PDF: The brazing adhesion properties of Ag coated W-Ag electric contact on the Cu substrate have been investigated in therms of microstructure, phase equilibrium and adhesion strength. Precoating of Ag layer (3µm in thickness) on the W-40%Ag contact material was done by electro-plating method. Subsequently the brazing treatment was conducted by inserting BCuP-5 filler metal (Ag-Cu-P alloy) layer between Ag coated W-Ag and Cu substrate and annealing at 710°C in H_2 atmosphere. The optimum brazing temperature of 710°C was semi-empirically calculated on the basis of the Cu atomic diffusion profile in Ag layer of commercial electric contact produced by the same brazing process. As a mechanical test of the electric contact after brazing treatment the adhesion strength between the electric contact and Cu substrate was measured using Instron. The microstructure and phase equilibrium study revealed that the sound interlayer structure was formed by relatively low brazing treatment at 710°C. Thin Ag electro-plated layer precoated on the electric contact (3µm in thickness) is thought to be enough for high adhesion strength arid sound microstructure in interface layer.

Effect of Annealing on Microstructural and Mechanical Property Variation of the Oxide-Dispersion-Strengthened Cu alloy: Yong-Suk Kim; J Korean Powder Metall Inst. 2006;13(1):25-32.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.025

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Abstract PDF: The alumina dispersion-strengthened (DS) C15715 Cu alloy fabricated by a powder metallurgy route was annealed at temperatures ranging from 800°C;to;1000°C in the air and in vacuum. The effect of the annealing on microstructural stability and room-temperature mechanical properties of the alloy was investigated. The microstructure of the cold rolled OS alloy remained stable until the annealing at 900°C in the air and in vacuum. No recrystallization of original grains occurred, but the dislocation density decreased and newly formed subgrains were observed. The alloy annealed at 1000°C in the air experienced recrystallization and grain growth took place, however annealing in vacuum at 1000°C did not cause the microstructural change. The mechanical property of the alloy was changed slightly with the annealing if the microstructure remained stable. However, the strength of the specimen that was recrystallized decreased drastically.

Effect of Cu content on Microstructure and Mechanical Properties of Al₂O₃/Cu Nanocomposites: Sung-Tag Oh, Se-Joong Yoon; J Korean Powder Metall Inst. 2006;13(1):33-38.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.033

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Abstract PDF: The effect of Cu content on microstructure and mechanical properties of nano-sized Cu dispersed Al_2O_3(Al_2O_3/Cu) nanocomposites was investigated. The nanocomposites with Cu content of 2.5 to 10 vol% were prepared by reduction and hot-pressing of Al_2O_3/CuO powder mixtures. The nanocomposites with Cu content of 2.5 and 5vol% exhibited the maximum fracture strength of 820MPa and enhanced toughness compared with monolithic Al_2O_3. The strengthening was mainly attributed to the refinement of Al_2O_3 matrix grains. The toughening mechanism was discussed by the observed microstructural feature based on crack bridging.

Microstructure and Mechanical Properties of Al/SiC_p Particle Reinforced Composite Severely Deformed by ARB Process: Seong-Hee Lee, Hyoung-Wook Kim; J Korean Powder Metall Inst. 2006;13(1):39-45.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.039

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Abstract PDF: The Al/SiC_p particle reinforced composite fabricated by a powder-in sheath rolling (PSR) method was severely. deformed by the accumulative roll-bonding (ARB) process. The ARB process was performed up to 8 cycles at ambient temperature without lubricant. The ARBed composite exhibited an ulbricant. grained structure similar to the other ARBed bulky materials. Tensile strength of the composite increased gradually with the number of ARB cycles, but from the 6th cycle it rather decreased slightly. These characteristics of the composite were somewhat different from those of Al powder compact fabricated by the same procedures. The difference in microstructure and mechanical properties between Al powder compact and the composite was discussed.

Fabrication of Sn and SnO₂ Nanopowders by Low-Temperature Phase Transformation Method: Kun-Jae Lee, Yeon-Jun Joo, Yong-Dae So, Nam-Hoon Kim, Jai-Sung Lee, Yong-Ho Choa; J Korean Powder Metall Inst. 2006;13(1):46-51.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.046

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Abstract PDF: Through the volume change of Sn in a low-temperature phase transformation, the Sn nanopowder with high, purity, was fabricated by an economic and eco-friendly process. The fine cracks were spontaneously generated. in, Sn ingot, which was reduced to powders in the repetition of phase transformation. The Sn nanopowder with 50 run in size was obtained by the 24th repetitions of phase transformation by low-temperature and ultrasonic treatments. Also, the SnO_2 powder was fabricated by the oxidation of the produced Sn powder to the ingot and milled by the ultrasonic milling method. The SnO_2 nanopowder of 20 nm in size was fabricated after the milling for 180 h.

On Apparent Density and Flow Rate Measurement at Elevated Temperature for Powder Mixes Intended for Warm Compacting: Jeong-Keun Lee, Soon-Wook Kim; J Korean Powder Metall Inst. 2006;13(1):52-56.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.052

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Abstract PDF: The aim of this work was to establish an optimal condition for determination of apparent density and flow rate for warm compacting powder. For this purpose it was evaluated uncertainty on them according to ISO Guide to the Expression of Uncertainty in Measurement. This evaluation example would be useful even in powder fluidity measurement at room temperature.

A new Aqueous Injection Molding Method of Fabricating W-Cu Pseudo-alloy Part: Jeong-Keun Lee; J Korean Powder Metall Inst. 2006;13(1):57-61.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.057

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Abstract PDF: The present work illustrates the use of water-soluble cupric salts as ingredients of binder for injection molding of W-10 wt% Cu. Parts produced are dense, homogeneous and have good surface finish, compared to those produced using conventional binder system. This new binder system provides also process-simplification benefit. CuCl_2;and;Cu(NO_3)_2 with the purity of 98% was selected for this study. Rapid sintering process involving thermal decomposing was successful in densification for 1h. Final density that is about 93% of theoretical value could be obtained, and are distinguishable from conventionally processed W-Cu composites.

Effect of Brake Timing on Joint Interface Efficiency of Aluminum Composites During Friction Welding: Hyun-Soo Kim, In-Duck Park, Takeshi Shinoda, Tae-Gyu Kim; J Korean Powder Metall Inst. 2006;13(1):62-67.; DOI: https://doi.org/10.4150/KPMI.2006.13.1.062

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Abstract PDF: Friction welding of Al_2O_3 particulate reinforced aluminum composites was performed and the following conclusions were drawn from the study of interfacial bonding characteristics and the relationship between experimental parameters of friction welding and interfacial bond strength. Highest bonded joint efficiency (HBJE) approaching 100% was obtained from the post-brake timing, indicating that the bonding strength of the joint is close to that of the base material. For the pre-brake timing, HBJE was 65%. Most region of the bonded interface obtained from post-brake timing exhibited similar microstructure with the matrix or with very thin, fine-grained Al_2O_3 layer. This was attributed to the fact that the fine-grained Al_2O_3 layer forming at the bonding interface was drawn out circumferentially in this process. Joint efficiency of post-brake timing was always higher than that of pre-brake timing regardless of rotation speed employed. In order to guarantee the performance of friction welded joint similar to the efficiency of matrix, it is necessary to push out the fine-grained Al_2O_3 layer forming at the bonding interface circumferentially. As a result, microstructure of the bonded joint similar to that of the matrix with very thin, fine-grained Al_2O_3 layer can be obtained.

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