• 한국재료학회지
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• 제23권3호
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• pp.199-205
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• 2013

The mechanical properties and microstructures of aluminum-matrix composites fabricated by the dispersion of fine alumina particles less than $20{\mu}m$ in size into 6061 aluminum alloys are investigated in this study. In the as-quenched state, the yield stress of the composite is 40~85 MPa higher than that of the 6061 alloy. This difference is attributed to the high density of dislocations within the matrix introduced due to the difference in the thermal expansion coefficients between the matrix and the reinforcement. The difference in the yield stress between the composite and the 6061 alloy decreases with the aging time and the age-hardening curves of both materials show a similar trend. At room temperature, the strain-hardening rate of the composite is higher than that of the 6061 alloy, most likely because the distribution of reinforcements enhances the dislocation density during deformation. Both the yield stress and the strain-hardening rate of the T6-treated composite decrease as the testing temperature increases, and the rate of decrease is faster in the composite than in the 6061 alloy. Under creep conditions, the stress exponents of the T6-treated composite vary from 8.3 at 473 K to 4.8 at 623 K. These exponents are larger than those of the 6061 matrix alloy.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.217-218
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• 2002

An integrated adhesive wear model was proposed to determine the transient wear and steady-state wear of aluminium alloy matrix composites. The transient wear volume was described by an exponential equation, while the steady-state wear was governed by a revised Archard equation, in which both the transient wear volume and transient sliding distance were excluded. A mathematical method was developed to determine both the transient distance and the net steady-state wear coefficient. Experimental wear tests were carried out on three types of commercial A6061 aluminum alloy matrix composites reinforced with 10%, 15% and 20% alumina particles. More accurate wear coefficient values were obtained with the proposed model. The average standard wear coefficient, as determined by the original Archard equation, was found to be about 51% higher.

• Journal of Advanced Marine Engineering and Technology
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• 제18권2호
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• pp.41-53
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• 1994

In this paper, rotating-bending fatigue tests of the SiC-whisker- reinforced 6061-T6 aluminum alloy and 6061-T6 alumiunm alloy made by power metallurgy were carried out to investigate the fatigue characteristics of plain and notched specimens at room temperature. The fatigue mechnisms in both materials were clarified through successive surface observations using the plastic replica method. In the case of the SiC-whisker-reinforced composites, there are whisker rich and poor zones and the fatigue crack is nucleated from the end of whiskers near the boundary. On the other hand, in the case of the 6061-T6 aluminum alloy, the fatigue crack is nucleated from defects and propagates by shear. Moreover, the results were discussed based on linear notch mechanics.

• Composites Research
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• 제33권5호
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• pp.241-246
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• 2020

본 연구에서는 교반주조 공정을 통해 B₄C 입자가 균일하게 분산된 알루미늄 금속복합재료를 제조하고 후 공정으로 열간압연을 수행하였다. 제조된 복합재료의 미세조직, 기계적 특성 및 내마모 특성에 대해 분석하였다. 40 ㎛ 크기의 B₄C 입자가 균일하게 분산된 복합재료는 강화재의 체적율이 증가함에 따라 인장강도는 증가하였으며, 마모 성능도 개선되었다. 20 vol.% 복합재료의 경우 인장강도 값은 292 MPa로 기지재인 Al6061 대비 155% 증가하였다. 내마모시험 결과 20 vol.% 복합재료의 경우 마모 너비와 깊이가 각각 856 ㎛, 36 ㎛이며, 마찰계수는 0.382로 Al6061 대비 상당히 우수한 내마모 특성을 나타내었다.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1223-1231
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• 2002

Al alloy matrix composite with TiNi shape memory fiber as reinforcement has been fabricated by hot pressing to investigate microstructures and mechanical properties. The analysis of SEM and EDS showed that the composites have shown good interface bonding. The stress-strain behavior of the composites was evaluated at temperatures between 363K and room temperature as a function of prestrain, and it showed that the yield stress at 363K was higher than that of the room temperature. Especially, the yield stress of this composite increases with increasing the amount of prestrain, and it also depends on the volume fraction of fiber and heat treatment. The smartness of the composite is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being prestrained. Microstructural observation has revealed that interfacial reactions occur between the matrix and fiber, creating two intermetallic layers.

• 한국분말재료학회지
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• 제16권3호
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• pp.209-216
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• 2009

A composite of rapidly solidified Al-6061 alloy powder with graphite particle reinforcements was prepared by ball milling and subsequent hot extrusion. The microstructure and mechanical properties of these composites were investigated as a function of milling time. With increasing milling time, the gas atomized initially and spherical powders became elongated with a maximum aspect ratio after milling for 30 h. Then, refinement and spheroidization were achieved by further milling to 70 h with a homogeneous and fine dispersion of graphite particles forming between the matrix alloy layers. The best compression and wear properties were obtained in the powder milled for 70 h, associated with the increased fine and homogeneous distribution of graphite particles in the aluminum alloy matrix.

• 한국정밀공학회지
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• 제10권3호
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• pp.152-160
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• 1993

This paper presents experimental study of the static and dynamic fracture toughness behavior of a A1-6061 aluminum alloy reinforced alumina( .delta. -A1$_{2}$0$_{3}$) whiskers with 5%, 10%, 15% volume fraction. The static fracture tests using three-point bending specimen were performed by UTM25T. And drop weight impact tester performing dynamic fracture tests was used to measure dynamic locads applied to a fatigue-precracked specimes. The oneset of crack initiation was detected uwing a strain gage bonded near a crack tip. The value of static fracture toughness $K_{IC}$ and dynamic fracture toughness $K_{ID}$ were decided on the basis of linear elastic fracture mechanics. The effects of fiber volume fraction and loading on fracture toughness were investigated. The distribution of whiskers, bonding state and fracture interfaces involved in void, fiber pull-out state were investigated by optical microscopy(OM) and scanning electron microscopy(SEM)

• 한국재료학회지
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• 제23권11호
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• pp.607-612
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• 2013

A powder in sheath rolling method was applied to the fabrication of a carbon nano tube (CNT) reinforced aluminum composite. A 6061 aluminum alloy tube with outer diameter of 31 mm and wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powder and CNTs with a volume content of 5% was filled in the tube by tap filling and then processed to an 85% reduction using multi-pass rolling after heating for 0.5 h at $400^{\circ}C$. The specimen was then further processed at $400^{\circ}C$ by multi-pass hot rolling. The specimen was then annealed for 1 h at various temperatures that ranged from 100 to $500^{\circ}C$. The relative density of the 5vol%CNT/Al composite fabricated using powder in sheath rolling increased with increasing of the rolling reduction, becoming about 97% after hot rolling under 96 % total reduction. The relative density of the composite hardly changed regardless of the increasing of the annealing temperature. The average hardness also had only slight dependence on the annealing temperature. However, the tensile strength of the composite containing the 6061 aluminum sheath decreased and the fracture elongation increased with increasing of the annealing temperature. It is concluded that the powder in sheath rolling method is an effective process for fabrication of CNT reinforced Al matrix composites.