• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.273-276
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• 2004

A356 alloy is one of the most popular casting aluminum alloys due to its good castability. It is well known that the mechanical properties of A356 alloy strongly depend on its characteristic microstructure, such as the size of eutectic Si, primary $\alpha$ dendrite and so on. These microstructural features are determined during the casting and solidification process, which implies the strong relationship with mechanical properties with solidification methods. In the present study, the mechanical characteristics of A356 alloy was investigated by using squeeze cast control arm in terms of the microstructural features, such as the size of eutectic Si, primary a dendrite. By doing so, the most favorable microstructure of A356 could be determined for Al control arm that should be one of the most reliable parts in automobile.

• 한국자동차공학회논문집
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• 제10권6호
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• pp.171-177
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• 2002

Metal matrix composites had generated a lot of interest in recent times because of significant in specific properties, it was also highlighted as the material of frontier industry because strength, heat-resistant, corrosion-resistant and wear-resistant were superiored. In recent years, the study of metal matrix composite has increased by aluminum alloy. The study is based on the tribological properties of AC4CH that is a part of the mechanical property of metal matrix composites. Metal matrix composite that is produced from matrix material AC4CH and reinforcement SiO$_2$, Al$_2$O$_3$ and TiO$_2$ are added to the metal matrix composite fur strength so binding among the whisker can take place. Each metal matrix composite is produced using the squeeze casting method. To test for tribe a pin-on-disk machine and lubricant is used without paraffine 8.2CST at room temperature which is 40$\^{C}$. As the results of this study, the tribological properties of each specimen are more improved than AC4CH. The variation of coefficient resistance is more stable at the AC4CH and TiO$_2$, but the variation rates are higher at the inanimate binder.

• 한국주조공학회지
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• 제15권2호
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• pp.138-145
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• 1995

The mechanical properties of $Al/Al_2O_3$ composites have been investigated in relation with manufacturing factors such as applied pressure of casting and binder amount of preform. It was found that tensile strength increases with an increase of applied pressure, but decreases with binder amount. Increase of tensile strength is attributable to refinement of microstructure, improvement of intefacial bonding between $Al_2O_3$ short fiber and matrix, decrease of porosity in the matrix. Due to the high thermal stability of alumina short fiber, tensile strength of composites at $150^{\circ}C$ was superior to matrix alloy at room temperature. To evaluate the strength of composites, modified Kelly-Tyson's equation was introduced. Manufacturing factor M was obtained calculating from experimental data. M values were increased with applied pressure, but decreased with binder amount. The initiation of microcrack appeared to be at interface and reinforcement colony. Amount of micro-dimple was increased with applied pressure, and interfacial debonding phenomenon was remarkable with an increase of binder amount.

• 한국추진공학회지
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• 제4권1호
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• pp.65-73
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• 2000

금속기지 복합재료의 주조는 폭넓은 재료의 선택과 공정조건들을 제공하는 좋은 공정이다. 용탕교반기술은 압착주조 또는 분말야금과 비교하면 매우 간단하고 값이 싸기 때문에 주조방법중에서 산업응용에 가장 널리 쓰이는 좋은 방법이다. 최근에는 $\alpha$ -$Al_2O_{3(p)}$/Lo-Ex alloy 복합재료의 입자크기, 입자의 부피 분율, 기계적 성질에 있어서 Mg첨가 그리고 열팽창계수 등이 연구되어 왔다. $\alpha$ -$Al_2O_3$는 입자계면과 기지에 형성되어 기계적 성질에 중요한 역할을 하였다 대부분 복합재료의 인장강도는 증가하지 않지만 16$\mu\textrm{m}$ $\alpha$ -$Al_2O_3$ 입자를 5vol%로 첨가한 경우, 3wt.% Mg를 첨가한 복합재료의 인장강도는 증가한다. 강화재의 부피분율과 mg은 복합재료의 열팽창계수를 감소시켰다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.155-160
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• 2002

Metal matrix composites had generated a lot of interest in recent times because of significant in specific properties. It was also highlighted as the materials of frontier industry because strength, heat-resistant, corrosion-resistant, wear-resistant were superiored. In this study the strength properties of $Al_{18}B_4O_{33}/AC4CH$ were represented mixing the binder of $Al_2O_3$ and $TiO_2$. It was also fabricated by squeeze casting. $Al_{18}B_4O_{33}/AC4CH$ was fabricated at the melt temperature of $760^{\circ}C$ the perform temperature of $700^{\circ}C$ and mold temperature of $200^{\circ}C$ under the pressure of 83.4MPa and observed SEM. Fatigue crack growth rate tests on compact tension specimen(half-size) of thickness 12.5mm were conducted by using sinusoidal waveform. Compact tension specimens(half-size) were used and fatigue crack growth rate da/dN and stress intensity factor range ${\Delta}K$ were analyzed concerning to the R value of 0.1 and 0.05. In order to find out the value of ${\Delta}K$, load amplitude constant method was applied by the standard fatigue testing method describes in ASTM E647-95a. As the results of this study, Fatigue crack growth rate increased with in creasing the load ratio, Consequently, At equivalent stress intensity factors, the fatigue crack growth rates in MMC were faster than those of AC4CH alloy. then the fatigue life and the fatigue crack growth rate was investigated using scanning election microscopy(SEM)

• 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.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 춘계학술발표 개요집
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• pp.155-159
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• 1995

A16061 alloy reinforced with 10 vol% $\delta$-A1$_2$O$_3$ short fiber have been fabricated by Rheo-compocasting and squeeze casting and extruded at high temperature using conical shape die and curved shape die with various extrusion ratios.. Tensile and hardness tests were carried out to examine mechanical properties of extruded materials and SEM observation of fractured surface was capable of accounting for fracture mechanism and bonding state of fiber and matrix.

• 한국주조공학회지
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• 제23권1호
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• pp.30-39
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• 2003

Porous hybrid preforms were fabricated by reactive sintering using the compacts consisting of SiC particles, Fe and Al powders. Squeeze casting processing was employed to produce the composite in which the matrix phase is Al-Si7Mg. The microstructural change and wear resistance of the composites were investigated in terms of an amount of SiC particles. The wear loss was increased with increasing the contact pressure in the alloy containing SiC particles coated with Cu. The most drastic change was found to the specimen tested at 2.5 MPa of contact pressure. Concerning the alloys containing SiC particles coated with Ni-P, a drastic increase in the wear loss exhibited at 2 MPa of contact pressure in those alloys containing 4 and 8 wt. % of SiC particles coated with Ni-P. In the alloy containing 16 wt. % a proportional increase in wear loss was observed to the change of contact pressure. With respecting to the sliding velocity, the wear loss of the alloy containing SiC particles coated with Cu increased at the initial stage of wear process and then decreased. Similar result was found in the alloys containing SiC particles coated with Ni-P. On the basis of the present results obtained, it was found that wear resistance of the alloys tested was improved to show in the order of the alloy reinforced by coated SiC particles > by uncoated SiC particles > by intermetallic compound without SiC particles.

• 한국주조공학회지
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• 제17권5호
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• pp.419-425
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• 1997

용탕단조방법에 의해 제조된 Mg-6Al-xZn(x=0, 1, 2)합금의 기계적 성질에 미치는 시효열처리의 영향을 조사한결과 아래와 같은 결론을 얻었다. (1) 주조조직을 관찰한 결과 미세한 수지상조직을 나타냈으며 초정${\alpha}$, 과포화 ${\alpha}$, ${\beta}$상 등 세가지 상으로 구성되어 있었다. (2) Mg-6Al-xZn합금은 시효경화성을 나타내었으며 Zn의 첨가량이 증가할수록 전시효구간에서 경도값이 높게 나타났다. (3) 시효조직을 관찰한 결과 $200^{\circ}C$의 시효시에는 불연속 석출물이 대부분 차지했으나 $240^{\circ}C$의 시효온도에서는 수지상 경계에서 시작되는 미세분산된 연속석출물이 대부분 이었다. (4) $240^{\circ}C$에서 시효열처리 한 시편은 연속석출물이 석출됨으로서 $200^{\circ}C$에서의 시효열처리된 시편에 비하여 과시효되는 경향이 작았다. (5) T6열처리 후 인장시험 결과 Zn 첨가량에 따라 강도가 증가하였는데 Mg-6Al-2Zn합금의 경우 인장강도는 248.4 MPa을 나타내었으며 Zn양에 따른 연신율의 감소는 나타나지 않았다.

• 대한기계학회논문집
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• 제17권7호
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• pp.1740-1750
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• 1993

The aluminar short fiber reinforced composite materials for hot extrusion were fabricated by semi-solid stirring method, and extruded at extrusion temperature $400^{\circ}C$ with various extrusion ratio. The hot extrusion load of volume fraction 15% metal matrix composites and base alloy Al7075 has been compared. The fiber length distribution, fiber breakage and fiber orientation are investiged to know the fiber behaviour in before and after hot extrusion. The tensile strength of the hot extruded billet are experimentally determined for different of extrusion ratios, and compared with theorically calculated strength.