• Advanced Composite Materials
• /
• v.18 no.4
• /
• pp.339-350
• /
• 2009

Al-Fe-V-Si alloys reinforced with SiC particles were prepared by multi-layer spray deposition technique. Both microstructures and mechanical properties including hardness and tensile properties development during hot exposure process of Al-8.5Fe-1.3V-1.7Si, Al-8.5Fe-1.3V-1.7Si/15 vol% $SiC_P$ and Al-10.0Fe-1.3V-2Si/15 vol% $SiC_P$ were investigated. The experimental results showed that an amorphous interface of about 3 nm in thickness formed between SiC particles and the matrix. SiC particles injected silicon into the matrix; thus an elevated silicon concentration was found around $\alpha-Al_{12}(Fe,\;V)_3Si$ dispersoids, which subsequently inhibited the coarsening and decomposition of $\alpha-Al_{12}(Fe,\;V)_3Si$ dispersoids and enhanced the thermostability of the alloy matrix. Moreover, the thermostability of microstructure and mechanical properties of Al-10.0Fe-1.3V-2Si/15 vol% $SiC_P$ are of higher quality than those of Al-8.5Fe-1.3V-1.7Si/15 vol% $SiC_P$.

• Journal of Life Science
• /
• v.16 no.2 s.75
• /
• pp.225-230
• /
• 2006

To elucidate the effect of temperature on the fruit body growth and structure of pleurotus ostreatus cultivar Chunchu No.2, microstructures were observed with scanning- and transmission electron microscope. Pileocystidia were well developed on the surface of pileus in the fruit body cultivated at $7^{\circ}C$. As the increasing temperature for fruit body development, thickness of pileus, thickness of stipes and length of stipes shown thin, thick and long, respectively. Color of pileus was also changes to whitish grown under high temperature. Physical structure shown as hardness and gumminess of stipes grown at high temperature, fruit body were soften than that of low temperature. Microstructures of fruit body grown at high temperature shown fast-discharge of basidiospore and sytoms aging. vacuolation in the cell observed at mycelium grown under high temperature. Optimum temperature for vegetative growth of fruit bodies were $15^{\circ}C$, and shown regular arrangement of mycelium on the surface of stipes.

• Journal of the Korean Ceramic Society
• /
• v.35 no.9
• /
• pp.939-944
• /
• 1998

The formation microstructure and properties of novel ceramic composite materials by active filler con-trolled polymer pyrolysis were investigated. Polymethlsiloxane filled with W is of particular interested be-cause of the formation of ceramic bonded hard materials (WC-$W_{2}C$-$S_{1}OC$) for wear resistant applications. Highly metal-filled polymer suspensions were prepared and their conversion to ceramic composites by an-nealing in $N_{2}C$ atmosphere at 1000-$1600^{\circ}C$ were studied. Dimensional change porosity and phase distribution (filler network) were analyzed and correlated to the resulting material properties. Microcrystalline com-posites with the filler reaction products embedded to the resulting material properties. Microcrystalline com-posites with the filler reaction products embedded in a silicon oxycarbide glass matrix were produced. De-pending on the pyrolysis conditions ceramic composites with a density up to 95 TD% a hardness of 7-8.8GPa Yong's modulus of 220-230 GPa a fracture toughness of 6-6.8$MPam^{1/2}$ and a flexual strength of 380-470 MPa were obtained.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.1
• /
• pp.111-116
• /
• 1998

Silicon nitride is hard and tough ceramic material. Hereby, mechanical machinability is very poor. It has also high electrical resistance. Silicon nitride of extremely high electrical resistivity becomes conductive ceramic composite by adding 30 wt% TiN. Ceramics with high electrical conductivity can be electrical discharge machined. Using by the Electrical Discharge Machining (EDM) technique. $Si_3N_4-TiN$ ceramic composite with high electrical conductivity is utilized to make metal working tool. These tool materials have severe wear problem as well as oxidation. Post HIP processing after sintering $Si_3N_4-TiN$ ceramic composites was performed. The tribological property of $Si_3N_4-TiN$ composite as a function of content of TiN was investigated in air, at room temperature. The hardness, fracture toughness, and flexural strength were compared with the wear volume. SEM observation of wear tracks can make an explanation of wear mode of $Si_3N_4-TiN$ composite.

• Composites Research
• /
• v.33 no.5
• /
• pp.251-255
• /
• 2020

In this study, TiC ceramic particulate reinforced steel composites was fabricated using a liquid pressing infiltration process. Studies were conducted on microstructure analysis and basic physical properties such as hardness and corrosion characteristics in salt water environment for comparison with commercial nodular cast iron. As a result of comparison of corrosion characteristics in a salt water environment, both corrosion potential and corrosion current density were lower than that of ductile graphite cast iron. The lower calculated corrosion rate confirms that the TiC-Fe metal composite has superior corrosion resistance than the cast iron.

• Journal of the Korean Society for Heat Treatment
• /
• v.33 no.3
• /
• pp.99-106
• /
• 2020

Selective laser melting (SLM) is an additive manufacturing process by melting metallic powders and stacking into layers, and can product complex shapes or near-net-shape (NNS) that are difficult to product by conventional processes. Also, SLM process is able to raise the efficiency of production by creating a streamlined manufacturing process. For manufacturing in SLM process using Ti-6Al-4V powder, analysis of microstructural evolution and evaluation of mechanical properties are essential because of rapid melting and solidification process of powders according to high laser power and rapid scan speed. In addition, it requires a post-processing because the soundness and mechanical properties are degraded by defects such as pore, un-melted powder, lack-of-fusion, etc. In this study, hot isostatic press (HIP) was conducted as a post-processing on SLM-printed Ti-6Al-4V alloy. Microstructure of post-processed Ti-6Al-4V alloy was compared to as-built Ti-6Al-4V, and the evolution of quasi-static (Vickers hardness, room temperature tensile characteristic) and dynamic (high-cycle fatigue characteristic) mechanical properties were analyzed.

• Laser Solutions
• /
• v.7 no.2
• /
• pp.1-10
• /
• 2004

This work was attempted to join SCP sheet and STS304 sheet by using Nd:YAC laser beam. SCP sheet has good formability and low cost, while STS304 has excellent corrosion resistance and mechanical properties in high temp. In this experiment, butt joint type was used to develop the tailored blank welding for dissimilar steel. Sheets which have different thermal properties. Computer simulation was conducted to obtain the off-set position for efficient welding by considering laser power, scanning speed, focal length and basic properties. The result showed that the optimum thermal distribution was obtained when the laser beam was irradiated at $0.05{\sim}0.1$ mm off-set toward the SCP sheet side. The experiment was conducted based on the result of computer simulation to show the same optimum conditions. Optimum conditions were 3KW in laser beam power, 6m/min in scanning speed, -0.5mm in focal position, 0.1mm off-set toward SCP. Microhardness test, tensile test, bulge test, optical microscopy, EDS, and XRD were performed to observe the microstructure around fusion zone and to evaluate the mechanical properties of optimum conditions, The weld zone had high microhardness values by the formation of the martensitic structure. Tensile test measured the strength of welded region by vertical to strain direction and the elongation of welded region by parallel to strain direction. Bulge test showed $52\%$ formability of the original materials. Bead shape, grain size, and martensitic structure were observed by the optical microscopy in the weld zone. Detailed results of EDS, XRD confirmed that the welded region was connected of martensitic structure.

• Journal of Animal Science and Technology
• /
• v.62 no.4
• /
• pp.577-586
• /
• 2020

This study was to investigate the effect of salt alone or in combination with phosphate on physicochemical and textural properties, and chemical interactions of low-fat model sausages. pH, color, expressible moisture (EM), cooking loss (CL), proximate analysis, textural profile analysis and low-vacuum scanning electron microscopy were performed. As salt content increased, color tended to decrease, as did EM and CL parameters, indicating that the ability to retain moisture was improved with increased salt levels (p < 0.05). In addition, textural hardness, gumminess and chewiness all increased with increasing salt (p < 0.05). Sausages with 0.3% salt showed the lowest cohesiveness compared to those with salt levels higher than 0.3% (p < 0.05). Addition of sodium tripolyphosphate (STPP) increased pH of sausages. Increasing salt and STPP did not affect lightness (p > 0.05), but did increase redness and yellowness (p < 0.05). The moisture content was higher when the salt and STPP contents were increased (p < 0.05), but no differences in the fat and protein contents (%) were observed (p > 0.05). EM and CL tended to decrease with increasing salt and STPP. In textural properties, the combination of 1.8% salt and 0.3% STPP was the best among other treatment (p < 0.05). Surface microstructure showed a flat and dense structure with increasing salt and STPP. Since the addition of salt and phosphate improved the functionality, textural and physicochemical properties of meat products in this study, meat products will need to be developed in line with consumer's preference.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.3
• /
• pp.231-237
• /
• 2000

The commercial cermet cutting tools consist of multi-carbide and a binder metal of iron group, such as cobalt and nickel which are ferromagnetic. In this paper, a new approach to evaluate the mechanical properties of TiCN based cermet by magnetic properties were studied in relation to binder content and sintering conditions. The experimental cermet was prepared using commercial composition with the other binder contents by PM process. It was found that the magnetic properties of the sintered cermets remarkably depended on the microstructure and the total carbon content. The magnetic saturation was proportional to increment of coercive force. At high carbon content in sintered cermet, the magnetic saturation was increased by decreasing the concentration of solutes such as W, Mo, Ti in Co-Ni binder. As the coercive force increases, the hardness usually increases. The strength and toughness of the cermet also increased with increasing the magnetic saturation. The measurement of magnetic properties made it possible to evaluate the mechanical properties in the cermet cutting tools.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1398-1401
• /
• 2005

The nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in squeeze-cast A356 alloy were investigated using nano/micro-indentation and mechanical scratching, combined wit optical microscopy and atomic force microscope(AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. In addition, the eutectic region showed lower pile-up and higher elastic recovery than the primary Al region. The aging responses of the eutectic regions in the squeeze-cast A356 alloys aged at $150^{\circ}C$ for different times(0, 2, 4, 8, 10, 16, 24, 36 and 72 h) were investigated. As the aging time increased, acicular Si particles in the eutectic regions gradually came to a fine structure. Both Vickers hardness ($H_V$) and indentation ($H_{IT}$) test results showed almost the same trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.