• Journal of the Korean Ceramic Society
• /
• v.31 no.8
• /
• pp.849-860
• /
• 1994

The microstructural evolution and crystalline phases of this infiltration of Ti+Al liquids in TiC, SiC, TiC+C, and SiC+C preforms have been investigated. As the Ti and Al mixing ratio in Ti+Al infiltrated liquid changes, the newly formed reaction products, which were reacted from the Ti+Al liquid with preforms, consisted of three major phases as Ti3AlC, Al2Ti4C2 or Al4C3. The TiC grain shape was changed to spheroid, when Ti3AlC was formed. In case of Al2Ti4C2 formation, the platelet grain was formed from the original TiC grain. When Al4C3 was formed, nodular or intergranular fine-grained Al4C3 was formed around the TiC grain, while the original TiC grain shape was not changed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.05a
• /
• pp.120-126
• /
• 2003

Finite element analysis model is suggested for analysis of milli-forming process, which forms milli-size products. Since the size of workpiece in a milli-forming process ranges from a few hundred micrometers to a few millimeters, microstructural changes such as the growth of micro-voids and the development of preferred orientation in a grain become crucial factors for the success of milli-forming. This analysis model incorporates anisotropy from deformation torture and deterioration of mechanical properties due to the growth of micro-voids. Applications of the proposed modeling to milli-forming are given and the results are carefully examined to understand the deformation characteristics such as texture development and damage evolution during extrusion/drawing of a milli-bar.

• Journal of the Korean Ceramic Society
• /
• v.35 no.4
• /
• pp.413-419
• /
• 1998

${\beta}$-silicon carbides with yttrium aluminum garnet of 2,5,10 mol% were prepared by a liquid--phase sint-ering and the microstructural evolution and phase transformation were investigated during sintering as functions of liquid-phase amount and sintering time. The rate of grain growth decreases with the addition of the amount of yttrium aluminum garnet (YAG) in the SiC starting powder however the apparent density and the aspect ratio of grains in sintered body increase. The phase transformation from ${\beta}$-SiC to ${\alpha}$-SiC were dependent on the liquid-phase amount and sintering time.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.10
• /
• pp.1087-1090
• /
• 2009

A unique process was developed to improve the mechanical properties of a circular tube. In this proposed process, a large amount of strain is applied to the wall of tube, leading to grain refinement in the material. In order to investigate characteristics of microstructural evolution such as the distribution of grain size and misorientation angle during the process, an EBSD OIM analysis was carried out. The analysis confirms that the proposed process can very effectively produce a circular tube with ultrafine-grains.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.3
• /
• pp.285-291
• /
• 2008

We have experimentally investigated the cyclic deformation in copper using ultrasonic nonlinearity. The observation and characterization of dislocation substructure have been conducted using transmission electron microscope and electron backscattered diffraction technique. The ultrasonic nonlinearity (${\beta}/{\beta}_0$) was measured by the harmonic generation technique after various fatigue cycles. The microstructural effect on the nonlinearity was discussed regarding the extent of dislocation substructures evolved from low cycle fatigue. The ultrasonic nonlinearity of copper monotonically increased with the fatigue cycles due to the evolution of dislocation cell substructures.

• Advances in environmental research
• /
• v.6 no.4
• /
• pp.255-264
• /
• 2017

This work investigated the use of sugarcane bagasse ash (SCBA) generated by an energy cogeneration process in sugarcane mill as an alternative raw material in soil-cement brick. The SCBA obtained from a sugarcane mill located in southeastern Brazil was characterized with respect to its chemical composition, organic matter content, X-ray diffraction, plasticity, and pozzolonic activity. Soil-cement bricks were prepared by pressing and curing. Later, they were tested to determine technical properties (e.g., volumetric shrinkage, apparent density, water absorption, and compressive strength), present crystalline phases, and microstructural evolution. It was found that the SCBA contains appreciable amounts of silica ($SiO_2$) and organic matter. The results showed that the SCBA could be used in soil-cement bricks, in the range up to 30 wt.%, as a partial replacement for Portland cement. These results suggest that the SCBA could be valorized for manufacturing low-cost soil-cement bricks.

• 한국초전도학회:학술대회논문집
• /
• v.9
• /
• pp.397-400
• /
• 1999

We have fabricated BSCCO 2223 by modified two powder process and investigated 2223 phase formation and grain growth. Phase evolution and reactivity of 2223 were remarkably sensitive to size of 2212 grains and liquid phase. Larger size of 2212 phase increased liquid formation temperature. The Avrami relation was well suited for describing the kinetics of grain growth in BSCCO 2223.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2000.10a
• /
• pp.21-24
• /
• 2000

Ultra-fine grains were produced in pure Al using an Accumulative Rolling-Bonding (ARB) process. After several cycles of the ARB process, pure Al sheets were filled with the ultra-fine grains whose diameters were several hundred nano-meters. With ARB cycles, the nature of grain boundaries of the ultra-fine grains changed from diffusive sub-boundaries to well-defined high angle boundaries. After 7 cycles, ultra-fine polycrystals with large misorientations between neighboring grains were obtained. Sliding wear tests using a pin-on-disk type wear tester were co ducted on the ultra-fine grained pure Al. Wear rates of pure Al increased with the increase of ARB cycle numbers in spite of the increase in hardness. Worn surfaces and cross-sections were examined with optical microscopy (OM) and scanning electron microscopy (SEM) In investigate the wear mechanism of the ultra-fine grained pure Al.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.168-171
• /
• 2006

Hot deformation behavior of A350 LF2 alloy was characterized by compression tests in the temperature range of 800-$1250^{\circ}C$ and the strain rate range of $0.001-10s^{-1}$. The microstructural evolution during hot compression was investigated and deformation mechanisms were analyzed by constructing processing map. Processing maps were generated using the dynamic material model (DMM). The combination of dynamic material model and Ziegler's instability criterion was applied to predict an optimum condition and unstable regions for hot forming.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.215-218
• /
• 2006

A study was made to investigate microstructural evolution and mechanical properties of ultra-fine grained (UFG) pure-Ti produced by equal channel angular (ECA) pressings. The deformed structures were analyzed by finite element method and transmission electron microscopy with the increment of straining. After 4 isothermal ECA pressings, initial coarse grains ($30{\mu}m$) were significantly refined to ${\sim}0.3{\mu}m$ with homogeneous distribution of microstructure which was resulted from $180^{\circ}$ rotation of the sample between pressings. UFG pure-Ti exhibited the considerable improvement in yield strength while losing strain hardening capacity as compared to coarse grained microstructure at ambient temperature, which was mainly attributed to ultra-fine grain microstructure with non-equilibrium grain boundaries.