Akira Kitahara

ALPORAS Aluminum Foam: Production Process, Properties, and Applications

The production of foamed aluminum has long been considered difficult to achieve because of problems such as the low foamability of the molten metal, the varying size of the cellular structures, and solidification shrinkage. Researchers have gradually solved these problems and some manufacturers are now producing foamed aluminum by their own methods. Shinko Wire has been manufacturing foamed aluminum under the registered trade name ALPORAS since 1986, using a batch casting process.

Fabrication of carbon fibre-reinforced aluminium composites with hybridization of a small amount of particulates or whiskers of silicon carbide by pressure casting

An investigation was carried out on the fabrication of carbon fibre-reinforced aluminium matrix composites with hybridization of particulates or whiskers of silicon carbide by pressure casting. A small amount of particulates or whiskers was uniformly distributed among carbon fibres and the preforms prepared from the treated fibres were directly infiltrated by molten aluminium under applied stress. It was found that the longitudinal tensile strengths of hybrid composites were greatly improved, although their fibre volume fractions were very low compared to those of conventional composites. With this hybridization method, it is also practical to tailor the fibre volume fraction of composites from 60 to 25 vol %, which is not possible in direct infiltration of fibre preforms by pressure casting. The results obtained lead to the conclusion that particulate or whisker additions act not directly as reinforcements but as promoters to improve the infiltration performances of fibre preforms, and consequently to increase the strength-transfer efficiency of carbon fibres. The addition of particulates or whiskers can also improve other properties of the composites, such as hardness and wear resistance.

Aluminum Foam, “Alporas”: The Production Process, Properties and Applications

The production of foamed aluminum has long been considered difficult to realize because of such problems as the low foamability of molten metal, the varying size of cellular structures, solidification shrinkage and so on. Recently these problems have been solved by a number of researchers and some manufacturers produce foamed aluminum by their own methods. The authors have been employing a batch casting process and manufacturing foamed aluminum under the tradename ALPORAS{reg_sign} since 1986. This paper presents the manufacturing process, physical properties and some typical applications of ALPORAS.

Characteristics of several carbon fibrereinforced aluminium composites prepared by a hybridization method

The properties and microstructures of several high-strength and high-modulus carbon fibrereinforced aluminium or aluminium alloy matrix composites (abbreviated as HSCF/Al and HMCF/Al, respectively, for the two types of fibre) have been characterized. The composites evaluated were fabricated by pressure casting based on a hybridization method. It was found that the strength degradation of high-modulus carbon fibres after infiltration of aluminium matrices was not marked and depended upon the type of aluminium matrix. However, the strength of high-strength carbon fibres was greatly degraded by aluminium infiltration and the degradation seemed to be independent of the type of aluminium matrix. The longitudinal tensile strength (LTS) of CF/Al composites was very different between HMCF/Al and HSCF/Al composites. The HMCF/Al composites had LTS values above 800 MPa, but the HSCF/Al composites had only about 400 MPa. In contrast, the transverse tensile strength of the HSCF/Al composites, above 60 MPa, was much higher than that of the HMCF/Al composites, about 16 MPa. Chemical reactions were evident to the interface of high-strength carbon fibres and aluminium matrices. There was no evidence of chemical products arising between high-modulus carbon fibres and Al-Si alloy and 6061 alloy matrices. However, it was considered that some interfacial reactions took place in pure aluminium matrix composites. Fracture morphology observation indicated that the good LTS of CF/Al composites corresponded to an intermediate fibre pull-out, whereas a planar fracture pattern related to a very poor LTS and fibre strength transfer. The results obtained suggested that interfacial bonding between carbon fibres and aluminium matrices had an important bearing on the mechanical properties of CF/Al composites. An intermediate interfacial bonding is expected to achieve good longitudinal and transverse tensile strengths of CF/Al composites.

Hybridization with SiC particulates to control the fibre volume fraction and improve the longitudinal tensile strength of carbon fibre-reinforced aluminium composites

acad sinica,inst met res,shenyang 110015,peoples r china. nagasaki univ,dept mat sci & engn,nagasaki 852,japan.;cheng, hm (reprint author), govt ind res inst,tosu,saga 841,japan

Effect of silicon additions on characteristics of carbon fiber reinforced aluminum composites during thermal exposure

The effects of Si additions on the behavior of high modulus carbon fiber reinforced aluminum matrix (CF/Al) composites during thermal exposure at 773 K for different times have been investigated. The composites were fabricated via hybridization with a small volume fraction of SIC particles using a pressure-casting process, The change of longitudinal tensile strength, the strength degradation of carbon fibers, and the microstructural observations on the interfaces of CF/pure Al composites and CF/Al-Si composites after thermal exposure undoubtedly indicate that the alloying element Si in an aluminum matrix can effectively prohibit the interfacial reactions at the fiber/aluminum interface and has positive effects on the characteristics of CF/Al composites.

The tensile strength and fiber degradation of carbon fiber reinforced aluminium composites

govt ind res inst,tosu,saga 841,japan. nagasaki univ,dept mat sci & engn,nagasaki 852,japan.;cheng, hm (reprint author), acad sinica,inst met res,shenyang 110015,peoples r china

THE TENSILE-STRENGTH OF CARBON-FIBER REINFORCED 6061 ALUMINUM-ALLOY COMPOSITES IN AS-CASTED AND T6-TREATED STATES

GOVT IND RES INST,TOSU,SAGA 841,JAPAN. NAGASAKI UNIV,DEPT MAT SCI & ENGN,NAGASAKI 852,JAPAN.;CHENG, HM (reprint author), ACAD SINICA,INST MET RES,CHENYANG 110015,PEOPLES R CHINA

Estimation of contiguity for a monodispersed system of spherical particles

A new stereological method for the estimation of the contiguity (the degree of contact) for the monodispersed system of spherical particles is reported. Since this method is applicable to point-like contacts, the contiguity of ceramic particles can be evaluated in a metal matrix composite in which the contact is assumed to be point. The contiguity is derived from the geometrical calculation of centre-to-centre distance between particles, evaluation of contact, and consideration of the geometrical probability that two particles in contact are cut simultaneously by a test plane. The contiguity can be expressed by either the number of contacts per unit volume or the number of contacts per particle. Applying this method to a model material (Shirasu-balloon/aluminium alloy composite), the interrelations between the change in the contiguity and some physical properties of the material can be accurately explained.

Reaction between vitreous SiO2 and Al

Rate of reaction between Al and SiO2 in vitreous silica or in silicate was measured between 500°C and 600°C in air or vacuum. The reaction couples used in the study were aluminum-silica glass and aluminum-Shirasu Balloon, which was a hollow microsphere of aluminosilicate glass. In the present study, it was found that the rate determining stage of the reaction between SiO2 and Al was associated with breaking of a Si-O bond. Apparen+ activation energies of the reaction are 56.5cal/mol for the silica glass-aluminum system and 78.7cal/mol for the Shirasu Balloon-aluminum system, respectively.