• Journal of the Microelectronics and Packaging Society
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• v.26 no.2
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• pp.45-49
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• 2019

Herein we developed the hot extrusion technology to prepare n-type Bi-Te-Se-based thermoelectric materials with high reliability. Starting ingot was fabricated via melt-solidification process, then pulverized it into powders (${\sim}30{\mu}m$) by using high energy ball milling. By optimization of mold design and temperature-pressure conditions for hot extrusion, dense extrudate of 1.8 mm in diameter with high 00l orientation could be obtained from disc-shape compacted powders (20 mm in diameter). High power factor ${\sim}4.1mW/mK^2$ and enhanced mechanical strength ~50 MPa were simultaneously observed at 300 K.

• Journal of Korea Foundry Society
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• v.34 no.4
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• pp.123-129
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• 2014

This work presents the results of a thixo-extrusion process applied to aluminum alloy and and reheating characteristics of semi-solid A356 Alloy using have been discussed. The reheating experiment was performed using an electric resistance furnace and multi-stage heating for uniform reheating. The thixo-extrusion was performed at the optimal reheating conditions of the semi-solid A356 alloy, the the extrusion conditions were an extrusion ratio of 33 and ram speed of 6 mm/sec. The results showed that the thixo-extrusion of semi-solid A356 alloy fabricated by the cooling slope reduced the extrusion pressure by 180% in comparison with hot extrusion, and that a sound extrusion could be obtained in spite of the same extrusion ratio and strain rate.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.953-959
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• 1995

It was investigated that reinforced species, billet condition and extrusion variation in Al 6061 composite material effected on extrusion process of particulate reinforced composite material. The strength of composite material with reinforcement species revealed SiC$\sub$w/> A1$_2$O$\sub$3f/ > A1$_2$O$\sub$3f/ > A1$_2$O$\sub$3f/ orderly. K$\sub$w/ increased as volute fraction increased in all composite material. The composite materials reinforced by A1$_2$ $O_3$required the larger pressure in hot extrusion process than those by SiC$\sub$p/ at all condition. Extrusion process tended to decrease as the semi-angle of extrusion dies increased because larger contact area caused larger shear friction. Extrusion temperature went up about 50$^{\circ}C$ in low elevated deformation temperature. In extrusion temperature above 500$^{\circ}C$, severe tearing occurred on extrusion surface. More reinforcement in volume fraction, more hot tearing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1912-1920
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• 1997

In the analysis of metal forming process, ALE(Arbitrary Lagrangian Eulerian) finite element methods have been increasingly used for the capability to control mesh independently from material flow. The methods can be divided into two groups i.e., coupled and split formulations. In the present work, the split ALE formulation is used for computational efficiency. A split ALE finite element method developed for rigid-viscoplastic materials and applied to the analysis of hot square die extrusion. Since thermal state greatly affects the product quality, an ALE scheme for temperature analysis is also presented. As computational examples, profile shapes as square and cross-like sections are chosen.

• Transactions of Materials Processing
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• v.28 no.3
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• pp.123-129
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• 2019

Hypereutectic Al-Si alloys have been widely utilized for wear-resistant components in the automotive industry. In order to expand the application of Hypereutectic Al-Si alloys, the addition of alloying elements forming a stable precipitate at high temperature is required. Thermally stable inter metallic compounds can be formed through the addition of transition elements such as Fe, Ni to Al alloys. However, the amount of transition element to be added to Al alloys is limited due to their low solid solubility. Also, hypereutectic Al-Si-Fe alloys form coarse primary Si phases and needle-shaped intermetallic compounds during solidification in the general casting processes. In this study, the effects of the destruction of Intermetallic compound and Si phase are investigated via hot extrusion. Both the microstructure and mechanical properties are discussed under different extrusion conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.414-417
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• 2003

A copper-clad aluminium composite bar is lighter and less expressive than a commercial copper alloy bar. Copper-clad aluminium composite bar can be fabricated by hot hydrostatic extrusion process. In this work, the effect of die angle on the compressive properties of copper-clad aluminium composites fabricated using hydrostatic extrusion process was investigated experimentally. The results showed that optimum half die angle was in the range of 40$^{\circ}$ to 50$^{\circ}$ for an extrusion ratio of 19. The results also showed that the half die angle had little influence on the compressive strength of copper-clad aluminium composites. A diffusion layer increased with increasing die angle.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.14-19
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• 1996

This study presents development of finite element simulation program and analysis of hot extrusion through square dies with mandrel. The design of extrusion dies is still an art rather than science. Die design for a new extrusion is developed from through in-plant trials. In the present paper, three-dimensional steady-state finite element simulation program is developed. The developed system is effectively used to simulate extrusion of clamp shaped hollow section. The objective of the present paper is to study the possibility of integrating this method into the design of dies for extrusion of complex section. To obtain sound product, the distributions and effects of temperature, effective strain rate, mean strain rate and mean stress are studied.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.05a
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• pp.197-205
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• 1996

A combined extrusion process studied here consists of forward and backward extrusion, and it is formed in single operation. The metal flow involved in the operation has appeared to be difficult to analyze accurately because of mixed directions of the flow. In this study, conventional two operations of a forward and a backward extrusions is transformed into one operation of mixed extrusion. A process designed by an industry expert is simulated by the rigid-plastic finite element method to investigate the metal flow and defects. In addition to the FEM simulation, experimental analysis has been carried out to confirm the design in industry, which includes material characterization, preliminary expriment, and whole experimental forming operation. The experimental results show that warm forming of extrusion is more desirable than cold working and hot forming in view of grain growth. Also two conditions of lubrication between workpiece and die has been investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.266-269
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• 2005

The effect of exit temperature on the thickness of recrystallization layer during Al extrusion process was investigated. The recrystallization layer of an extruded Al alloy is an important feature of the product in a wide range of applications, particularly those within the automotive industry. The thicker recrystallized layer in the Al alloys can give rise to a number of problems including reduced fatigue resistance and orange peel during cold forming. But the interaction of extrusion process variables with the thickness of recrystallization layer is poorly understood, and there is limited information available regarding the role of the main hot extrusion variables. Using the 3650 US ton extrusion press, this paper describes the effect of the main process variables such as billet temperature, ram speed, and exit temperature on the thickness of recrystallization layer for the A6XXX Al alloy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1295-1296
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• 2013