간행물
한국분말야금학회지 KCI 등재 Journal of Korean Powder Metallurgy Institute
- 발행기관 한국분말재료학회(구 한국분말야금학회)
- 자료유형 학술지
- 간기 격월간
- ISSN 1225-7591 (Print)2287-8173 (Online)
- 수록기간 1994 ~ 2024
- 주제분류 공학 > 금속공학 공학 분류의 다른 간행물
- 십진분류KDC 559DDC 629
권호리스트/논문검색
Vol. 20 No. 4 (2013년 8월) 12건
1.
2013.08
구독 인증기관 무료, 개인회원 유료
This study attempted to manufacture a Cu-Ga coating layer via the cold spray process and to investigate the applicability of the layer as a sputtering target material. In addition, changes made to the microstructure and prop- erties of the layer due to annealing heat treatment were evaluated, compared, and analyzed. The results showed that coating layers with a thickness of 520 mm could be manufactured via the cold spray process under optimal conditions. With the Cu-Ga coating layer, the α-Cu and Cu3Ga were found to exist inside the layer regardless of annealing heat treatment. The microstructure that was minute and inhomogeneous prior to thermal treatment changed to homogeneous and dense with a more clear division of phases. A sputtering test was actually conducted using the sputtering target Cu- Ga coating layer (~2 mm thickness) that was additionally manufactured via the cold-spray coating process. Consequently, this test result confirmed that the cold sprayed Cu-Ga coating layer may be applied as a sputtering target material.
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2.
2013.08
구독 인증기관 무료, 개인회원 유료
Freeze drying for porous Mo was accomplished by using MoO3 powder as the source and camphor-naph- thalene eutectic system as the sublimable material. Eutectic composition of camphor-naphthalene slurries with the initial MoO3 content of 5 vol%, prepared by milling at 55o C with a small amount of oligomeric dispersant, was frozen at -25o C. The addition of dispersant showed improvement of dispersion stability in slurries. Pores were generated subse- quently by sublimation of the camphor-naphthalene during drying in air for 48 h. To convert the MoO3 to metallic Mo, the green body was hydrogen-reduced at 750o C, and sintered at 1100o C for 2 h. The sintered samples, frozen by heated Teflon cylinder, showed large pores with the size of about 40 µm which were aligned parallel to the sublimable vehicles growth direction. The formation of unidirectionally aligned pores is explained by the rejection and accumulation of solid particles in the serrated solid-liquid interface.
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3.
2013.08
구독 인증기관 무료, 개인회원 유료
We examined various ball-milling parameters which affect the structural and morphological modification of multi-wall carbon nanotubes. In particular, the effect of milling mode and the use of different milling agents were exam- ined. Friction milling mode induced more structural changes than impact milling mode except the use of dry ice as a milling agent. Wet milling was helpful for reducing more effectively the agglomeration of nanotubes than dry milling. The use of hard solid particles such as silica and alumina as milling agents resulted in an effective shortening of nan- otubes, but often susceptible to the amorphization and the destruction of crystallinity.
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4.
2013.08
구독 인증기관 무료, 개인회원 유료
Nickel-based superalloy IN 713C powders have been consolidated by hot isostatic pressing (HIPing). The microstructure and mechanical properties of the superalloys were investigated at the HIPing temperature ranging from 1030o C to 1230o C. When the IN 713C powder was heated above γ' solvus temperature (about 1180o C), the microstruc- ture was composed of the austenitic FCC matrix phase γ plus a variety of secondary phases, such as γ' precipitates in γ matrix and MC carbides at grain boundaries. The yield and tensile strengths of HIPed specimens at room temperature were decreased while the elongation and reduction of area were increased as the processing temperature increased. At 700o C, the strength was similar regardless of HIPing temperature; however, the ductility was drastically increased with increasing the temperature. It is considered that these properties compared to those of cast products are originated from the homogeneity of microstructure obtained from a PM process.
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5.
2013.08
구독 인증기관 무료, 개인회원 유료
The present work investigated the dispersion behavior of Y2O3 particles into AISI 316L SS manufactured using laser cladding technology. The starting particles were produced by high energy ball milling in 10 min for pre- alloying, which has a trapping effect and homogeneous dispersion of Y2O3 particles, followed by laser cladding using CO2 laser source. The phase and crystal structures of the cladded alloys were examined by XRD, and the cross section was characterized using SEM. The detailed microstructure was also studied through FE-TEM. The results clearly indi- cated that as the amount of Y2O3 increased, micro-sized defects consisted of coarse Y2O3 were increased. It was also revealed that homogeneously distributed spherical precipitates were amorphous silicon oxides containing yttrium. This study represents much to a new technology for the manufacture and maintenance of ODS alloys.
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6.
2013.08
구독 인증기관 무료, 개인회원 유료
Fe-based oxide dispersion strengthened (ODS) powders were produced by high energy ball milling, fol- lowed by spark plasma sintering (SPS) for consolidation. The mixed powders of 84Fe-14Cr-2Y2O3 (wt%) were mechanically milled for 10 and 90 mins, and then consolidated at different temperatures (900~1100o C). Mechani- cally-Alloyed (MAed) particles were examined by means of cross-sectional images using scanning electron micros- copy (SEM). Both mechanical alloying and sintering behavior was investigated by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). To confirm the thermal behavior of Y2O3, a replica method was applied after the SPS process. From the SEM observation, MAed powders milled for 10 min showed a lamella structure consisting of rich regions of Fe and Cr, while both regions were fully alloyed after 90 min. The results of sintering behavior clearly indicate that as the SPS temperature increased, micro-sized defects decreased and the den- sity of consolidated ODS alloys increased. TEM images revealed that precipitates smaller than 50 nm consisted of YCrO3.
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7.
2013.08
구독 인증기관 무료, 개인회원 유료
Stress-strain curves are fundamental properties to study characteristics of materials. Flow stress curves of the powder materials are obtained by indirect testing methods, such as tensile test with the bulk materials and powder compaction test, because it is hard to measure the stress-strain curves of the powder materials using conventional uniax- ial tensile test due to the limitation of the size and shape of the specimen. Instrumented nanoindentation can measure mechanical properties of very small region from several nanometers to several micrometers, so nanoindentation tech- nique is suitable to obtain the stress-strain curve of the powder materials. In this study, a novel technique to obtain the stress-strain curves using the combination of instrumented nanoindentation and finite element method was introduced and the flow stress curves of Fe powder were measured. Then obtained stress-strain curves were verified by the com- parison of the experimental results and the FEA results for powder compaction test.
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8.
2013.08
구독 인증기관 무료, 개인회원 유료
Ti2AlN composites are a laminated compounds that posses unique combination of typical ceramic proper- ties and typical metallic(Ti alloy) properties. In this paper, the powder synthesis, SPS sintering, composite characteristics and machinability evaluation were systematically conducted. The random orientation characteristics and good crystalli- zation of the Ti2AlN phase are observed. The electrical and thermal conductivity of Ti2AlN is higher than that of Ti6242 alloy. A machining test was carried out to compare the effect of material properties on micro electrical discharge drilling for Ti2AlN composite and Ti6242 alloy. Also, mixture table as a kind of tables of orthogonal arrays was used to know how parameter is main effective at experimental design. Consequently, hybrid Ti2AlN ceramic composites showed good machining time and electrode wear shape under micro ED-drilling process. This conclusion proves the feasibility in the industrial applications.
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9.
2013.08
구독 인증기관 무료, 개인회원 유료
SKD11 (ASTM D2) tool steel is a versatile high-carbon, high-chromium, air-hardening tool steel that is charac- terized by a relatively high attainable hardness and numerous, large, chromium rich alloy carbide in the microstructure. SKD11 tool steel provides an effective combination of wear resistance and toughness, tool performance, price, and a wide variety of product forms. The CNTs was good additives to improve the mechanical properties of metal. In this study, 1, 3 vol% CNTs was dispersed in SKD11 matrix by mechanical alloying. The SKD11+ CNT hybrid nanocomposites were investigated by FE-SEM, particle size distribution, hardness and wear resistance. The CNT was well dispersed in the SKD11 matrix and the mechanical properties of the composite were improved by CNTs addition. It shows good fea- sibility as cold work die tool.
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10.
2013.08
구독 인증기관 무료, 개인회원 유료
Mirror surface machining for large area flattening in the display field has a problem such as a tool wear and a increase in machining time due to large area machining. It should be studied to decrease machining time and tool wear. In this paper, multi-tool machining method using a PCD tool and a SCD tool was applied in order to decrease machining time and tool wear. Machining characteristics (cutting force, machined surface and surface roughness) of PCD tool and SCD tool were evaluated in order to apply PCD tool to flattening machining. Based on basic experi- ments, the PCD/SCD multi-tool method and the SCD single-tool method were compared through surface roughness and machining time for appllying large area mold machining.
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11.
2013.08
구독 인증기관 무료, 개인회원 유료
A5J32-T4 and A5052-H32 dissimilar aluminum alloy plates with thickness of 1.6 and 1.5 mm were welded by friction stir lap welding (FSLW). The FSLW were studied using different probe length tool and various welding conditions which is rotation speed of 1000, 1500 rpm and welding speed of 100 to 600 mm/min and material arrangement, respectively. The effects of plunge depth of tool and welding conditions on tensile properties and weld nugget formation. The results showed that three type nugget shapes such as hooking, void, sound have been observed with revolutionary pitch. This plunge depth and material arrangement were found to effect on the void and hooking for- mation, which in turn significantly influenced the mechanical properties. The maximum joint efficiency of the FSLWed plates was about 90% compared to base metal, A5052-H32 when the A5052-H32 was positioned upper plate and plunge depth was positioned at near interface between upper and lower plates.
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12.
2013.08
구독 인증기관 무료, 개인회원 유료
In this paper, we describe experiment results using a vibration assisted hybrid femtosecond laser (λ:795 nm) ultra- precision machining system. The hybrid system we have developed is possible that optical focal point of the femtosec- ond laser constantly and frequently within the range of PZT(piezoactuator) vibrator working distance. Using the hybrid system, We have experimented on brass and studied about differences of result of hole aspect ratio compare to general experiment setup of femtosecond laser system. Aspect ratio of a micro hole on brass is increased as 54% with 100 Hz vibration frequency and surface roughness of the side wall also improved compare to non-vibration.
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