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김홍물 한국분말야금학회 2000 한국분말재료학회지 (KPMI) Vol.7 No.2
A process has been successfully used to manufacture 6061/Graphite composite material and the Graphite particles are distributed uniformly within the Al alloy matrix. The 6061 powders was mixed with natural Graphite particles in a ball milling blender and cold compacted specimens were extruded into rods 15mm in diameter at 450$^{\circ}C$. The results showed that tensile properties of the composites with Graphite content have been reduced. The emergence of fine microstructures appeared to be related to the graphite volume. Heat-treated composites were found to possess good mechanical properties as compared with those of non heated composites. A model was used that the tensile strength of the composites would be estimated from the theoretical calculation and experimental data.
급속응고된 Al-Pb-Cu-Mg 합금의 마모특성에 미치는 미세조직의 영향
김홍물 한국분말야금학회 2000 한국분말재료학회지 (KPMI) Vol.7 No.1
Effects of the microstrucrure of rapidy solidified Al-Pb-Cu-Mg alloys on the wear investigated. In order to overcome the miscility gap between Al and pb under equilibrium conditions, both in the solid and the liquid states, the alloy were rapidy solidifies to produce them in a segregation-free condition. Although the Pb particles showed relatively fine dispersion in the Al matrix in all the alloys by this process. the Al-16Pb alloy was found to have the most favorable microstructure with discretre with discrete Pb particles of abount 0.5 ${\mu}$m in size. With the addition of Cu and Cu-Mg to Al-16Pb, cellular structures were newly formed; not seen in the binary Al-Pb alloy. Wear properties of the Al-Pb binary alloys measured as a function of the sliding speen, sliding distance, and applied load showed that the Al-16Pb alloy has the best wear resistance, as expected from the fine microstructural features in this alloy. The were resistance of the alloy containing Cu-and Cu-Mg was higher than that of the Al-16Pvb alloy, due to matrix strengthening by precipitation hardeing. The wear mechanism was identified by examining the traces and wear debris.
2024A1/$SiC_p$복합재료의 기계적특성에 미치는 SiC클러스터의 영향
김홍물,천병선 한국분말야금학회 2001 한국분말재료학회지 (KPMI) Vol.8 No.2
A centrifugally atomized 2024A1/SiC/sub p/ composites were extruded to study effect of clusters on mechanical properties, and a model was proposed that the strength of MMCs would be estimated from the load transfer model approach that taken into consideration of the clusters. This model has been successfully utilized to predict the strength and fracture toughness of MMCs. The experimental and calculated results show coincidence and that the fracture toughness decreases with increasing the volume fraction of particles. On the basis of experimental observations, we suggest that the strength and fracture toughness of particle reinforced MMCs may be calculated from; σ/sub y/=σ/sub m/V/sub m/+σ/sub r/(V/sub r/-V/sub c)-σ/sub r/V/sub c/, K/sub IQ/=σ/sub Y/((3πt)((r/sub r//V/sub r/)(r/sub c//V/sub c/))/sup 1/2/)/sup 1/2/, respectively.
고에너지 밀링공정을 이용한 조대 마그네슘 분말의 미세화 거동
송준우,김효섭,김홍물,김택수,홍순직,Song, Joon-Woo,Kim, Hyo-Seob,Kim, Hong-Moule,Kim, Taek-Soo,Hong, Soon-Jik 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.4
In this research, the refinement behavior of the coarse magnesium powders fabricated by gas atomization was investigated as a function of milling time using a short duration high-energy ball milling equipment, which produces fine powders by means of an ultra high-energy within a short duration. The microstructure, hardness, and formability of the powders were investigated as a function of milling time using X-ray diffraction, scanning electron microscopy, Vickers micro-hardness tester and magnetic pulsed compaction. The particle morphology of Mg powders changed from spherical particles of feed metals to irregular oval particles, then platetype particles, with increasing milling time. Due to having HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, resulting in producing plate-type powders. With increasing milling time, the particle size increased until 5 minutes, then decreased gradually reaching a uniform size of about 50 micrometer after 20 minutes. The relative density of the initial power was 98% before milling, and mechanically milled powder was 92~94% with increase milling time (1~5 min) then it increased to 99% after milling for 20 minutes because of the change in particle shapes.