• 한국해양공학회지
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• 제11권2호
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• pp.18-27
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• 1997

Al 6061 alloy reinforced with 10 vol.% ${\delta}-Al_2O_3$ short fiber was fabricated by Rheo-compocasting and squwwze cating. Extrusion processings were performed at temperatures from 40$0^{\circ}C$ to 55$0^{\circ}C$ with various extrusion ratio for curved shape dies. In proportion to the increase of extrusion ratios and temperatures, ultimate tensile strength for extruded materials improved. SEM observation of fractured surfsce was capcble oof accounting for fracture mechanism and bounding state of fiber and matrix.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1541-1550
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• 2001

This paper describes experimental investigations in the direct extrusion of copper clad aluminum rods through conical dies. Composite materials consist of two or more different material layers. Copper clad aluminum composite materials are being used fur economic and structural purposes and the development of an efficient production method of copper clad aluminum composite material rods by extrusion is very important, It is necessary to know the conditions in which successful uniform extrusion ,and sound cladding may be carried out without any defects in the direct extrusion. There are several variables that have an influence on determining a sound clad extrusion. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios and semi-cone angles of die. Subsequently, the microscopic inspection of interface bonding is carried out for extruded products. By measuring hardness, along extrusion way of products, a variation of hardness has been discussed. Proportional flow state has been considered by measuring radius ratio of Cu sleeve and Al core before and after extrusion.

• 한국주조공학회지
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• 제24권6호
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• pp.331-339
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• 2004

Melt-extrusion process, a metallic melt poured and solidified up to semisolid state in the container can be directly extruded through the die exit to form a product of bar shape without other intermediate processes. In this study, the fabrication characteristics of the process were evaluated with various process parameters, such as preheating temperature of extrusion dies, extrusion temperature and extrusion ratio. AI-Cu alloys were successfully extruded after squeezing out of liquid during melt-extrusion with smaller force compared to the solid extrusion. Soundly AI-Cu alloy bar was fabricated at the preheating temperature of $500{\sim}520^{\circ}C$. The range of extrusion temperature for soundly melt-extruded AI-Cu alloy bar was increased with increasing extrusion ratio. Mechanical properties of melt-extruded AI-Cu alloy bars were found change with Cu content of the melt-extruded bars due to the occurrence of segregation. The various extrusion temperature yielded equiaxed structure with a grains size about 200 ${\mu}m$.

• 한국주조공학회지
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• 제34권4호
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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.

• 한국분말재료학회지
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• 제2권1호
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• pp.44-52
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• 1995

Effects of the extrusion temperature and die angle on the tensile properties of SiCIyAl composites in powder extrusion have been investigated. SiCP/Al composites were extruded at various extrusion temperatures (450, 500, $550^{\circ}C$) under the extrusion ratio of 25 : 1. The ram speed was maintained at 13 cm/min for all the extrusion conditions. The surface of the extruded rod appeared to be smooth without tearing at 450 and 50$0^{\circ}C$, whereas it was very rough due to tearing at $550^{\circ}C$. It was found that the tensile strength and elongation of the composites extruded at $500^{\circ}C$ are greater than those of composites extruded at $450^{\circ}C$ This is due to the easier plastic deformation of composite extruded at $500^{\circ}C$, compared with the composites extruded at $450^{\circ}C$. The effect of die angle was examined under 20=60, 120, $180^{\circ}$die angles at extrusion temperature of $500^{\circ}C$ under 25:1 extrusion ratio. The tensile strength of the composites extruded with 20=$60^{\circ}$approved to be higher than that of the composties extruded with 28 : 120 and $180^{\circ}$This is attributable to the higher extrusion pressure, which mixed composite powders could be densely consolidated at elevated temperatures, resulting from high friction force between billet and sliding surface of conical die.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.144-147
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• 2005

In hydrostatic extrusion the billet in the container is extruded through a die with a liquid acting as a pressure medium, instead of by the direct application of the load by a ram. And the extrusion pressure can be affected by the flow stress and they are affected by the temperature. So in this study the temperature is the main issue with a extrusion ratio and a half die angle. As extrusion temperature goes down from $300^{\circ}C$ to $200^{\circ}C$, tensile strength goes up to 310MPa. Because velocity of extrusion is higher than the conventional extrusion, there is another characteristic in the sense of microstrure. The temperature was sotted to $300^{\circ}C,\;250^{\circ}C,\;200^{\circ}C$, respectively. There is a increase of extrusion pressure abot $15\%$.

• 소성∙가공
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• 제3권3호
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• pp.291-301
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• 1994

In the simultaneous forward-backward extrusion the effects of some process variables including area reduction, stroke advance, materials(Al 2024 and commercial pure copper) on the extrusion load, plastic flow and height ratio of upper to lower extruded parts are experimentally investigated and analyzed. Grid-marking technique is employed to visualize the plastic flow. The influence of using split and original specimen on the extrusion load and height ratio is evaluated by experiments. Experimental results show that the plastic flow if oriented to the part of lower area reduction in the begining but it is usually variated during the overall process. The configurations of plastic deformation and plastic flow are dependent on the working materials and the lubricational conditions.

• 한국정밀공학회지
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• 제21권7호
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• pp.179-184
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• 2004

In this work, a copper-clad aluminum composite was fabricated using hot hydrostatic extrusion with various extrusion ratios (8.5, 19, 49) and semi-die angles (30, 45, 60 degree) at a temperature of 32$0^{\circ}C$, Material characteristics of copper-clad aluminum composites were determined from compression tests and hardness tests The results showed that for ER of 8.5, the optimum semi-die angle was below or equal to 30 degree and a pressure drop was about 31%. For ER of 19, the optimum semi-die angle was in the range of 40 to 50 degree and a pressure drop was about 38%. In the case of ER=49, the optimum semi-die angle was above or equal to 60 degree and a pressure drop was about 36%. Compressive yield strength was maximum for ER of 8.5 and semi-die angle of 30 degree and the value of maximum was 155 MPa. Uniform hardness distribution was obtained as the extrusion ratio increases and the semi-die angle decreases. In the case of ER=8.5 and semi-die angle of 30 degree, the lowest extrusion pressure and the maximum compressive yield strength was obtained. Therefor, it was concluded that the optimum extrusion condition for fabricated copper-clad aluminum composites under hydrostatic pressure environment was ER of 19 and semi-die angle of 30 degree.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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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.

• 소성∙가공
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• 제15권8호
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• pp.597-602
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• 2006

Bulk plastic forming characteristics were studied for the magnesium alloy, AZ31 in warm backward extrusion. Effects of process conditions such as extrusion ratio, forming temperature, and punching speed were investigated respectively. Variation of microstructure induced by the warm backward extrusion process was observed. Microstructure of the work piece showed evidences of recrystallization under the experiment conditions. It is estimated that in specific punch speed region fast stroke accelerates recrystllization and reduces the forming load.