Moonhee Lee

Fabrication and characterization of unidirectional CF/Al composites

Abstract The unidirectional carbon fiber (CF) reinforced aluminum (Al) composites have been fabricated by the low pressure infiltration (LPI) of molten Al into porous CF preform. Prior to the fabrication of the unidirectional CF/Al composites, the unidirectional CF preform was prepared by sintering of CFs and copper (Cu) particles under the spark plasma sintering (SPS). The compression strength of CF preform was examined to determine the infiltration pressure of molten Al into CF preform. The effects of the different infiltration pressures and sizes of Cu particles on the densification of unidirectional CF/Al composites have also been investigated. The compression strength of CF preform increased with increasing of the contact area between CFs and Cu particles. The density of CF/Al composites improved with the increase of the infiltration pressure. The CF/Al composites, into which the bimodal Cu particles are added, have average particle sizes of 2.55 μm and 11.79 μm, with a high relative density of about 95% with the nearly homogeneous fiber distribution.

Effect of SiO2 amount on microstructures and tensile properties of alumina short fiber-reinforced composites by low-pressure infiltration method:

The tensile properties of two types of alumina (Al2O3 and Al2O3–SiO2) and short fiber-reinforced A366 alloy composite created by low-pressure infiltration have been studied. The applied pressure and temperature of molten alloy are 0.4 MPa and 1073 K, respectively. The composite containing 10 vol.% of fiber preform was sectioned and the microstructure was observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. Tensile properties of Al2O3 fiber-reinforced A366 alloy composites were investigated, in conjunction with investigation of effects of amounts of SiO2 sol added as binder to fabricated preform and effects of changed chemical composition of Al2O3 fiber. The composite with SiO2 sol of 8 mass% has higher relative density in comparison with composite with SiO2 sol of 2 mass%. SiO2 sol raised the relative density of composite by the reaction with aluminum. In addition, the ultimate tensile strength of composite which has Al2O3 fiber-reinforced A366 alloy composite containing SiO2 sol of 8 mass% was approximately 20% higher than that of Al2O3–SiO2 fiber-reinforced A366 alloy composite containing SiO2 sol of 8 mass%.

Influence of Si addition on thermal conductivity of unidirectional CF/Al-Si composites fabricated by low pressure infiltration process

Abstract Unidirectional CF/Al-Si composites were fabricated by low pressure infiltration, permeating molten Al into porous CF-Si preform. In this study, the influences of Si addition in the preforms on the thermal conductivity of obtained CF/Al-Si composites were investigated in terms of the degradation of high thermal conductive CFs by chemical reactions in Si-C and Al-C systems. Comparing with theoretical value, the thermal conductivity of CF/Al-Si composites was extremely low. Although the Si-C reaction led to the decrease of the thermal conductivity, the sintered Si around CF surfaces protected from the significant decrease of the thermal conductivity being attributed to the severe Al and CF reaction. The surface damage of high thermal conductive CFs by Al-C reaction became a main reason for the decrease in the thermal conductivity of CF/Al-Si composites. Especially, the active Al-C reaction in the region of extremely low Si content around CF surfaces affected significant degradation of the CFs.

Development of vapour-grown carbon nano-fibre-reinforced aluminium matrix composites by low-pressure infiltration process

Abstract This study was aimed for development of vapour-grown carbon nano-fibre(VGCNF)-reinforced aluminium matrix composites by the low-pressure infiltration process. First, VGCNF and Al powder (VGCNF + Alp) preforms for low-pressure infiltration were fabricated by spark sintering process at pressures of 5, 10, 20 and 40 MPa, respectively. Porosity of the preforms fabricated at pressures of 5 and 10 MPa was 44·89 and 40·87%, respectively. However, porosity of the preforms fabricated by spark sintering at pressures of 20 and 40 MPa was approximately 20%. Therefore, VGCNF + Alp/Al composites with the preform sintered at pressures of 5 and 10 MPa were fabricated by the low-pressure infiltration process under an applied pressure of 0·4 MPa, and the relative density was 81·4 and 76·0%, respectively. Moreover, the microstructure, porosity and electrical conductivity of the VGCNF + Alp/Al composites were estimated. Their electrical conductivities reduced with increasing porosity of VGCNF + Alp/Al composites.

Manufacturing Process of Celmet Reinforced Aluminum Alloy Composite by Low‐Poressure Casting

A new process is proposed to fabricate an intermetallic compound, Al3Ni particles reinforced aluminum alloy matrix composite using the reaction between nickel celmet and molten aluminum. The intermetallic compound, Al3Ni particles reinforced aluminum alloy composite was manufactured with the low-pressure infiltration process method. Nickel celmet reacted with molten aluminum at 973K, and the intermetallic compound of Al3Ni was generated on the surface of the nickel celmet. The generated intermetallic compound, Al3Ni obtained the result which delamination from the surface of a nickel celmet and it distributes into the portion of aluminum matrix. The effects of processing variables, such as cooling rate and specific surface area of nickel celmet on the formation and dispersion behavior of Al3Ni were investigated