Aluminium–aluminium nitride composites fabricated by melt infiltration under pressure

Abstract

Aluminium-matrix composites containing approximately 55 vol.% AlN particles were fabricated by melt infiltration of aluminium into an AlN preform under a pressure of up to 130 MPa. Two different AlN powders (H.C. Starck, Goslar, Germany, and ESK, Elektroschmelzwerk, Kempten, Germany) and four types of aluminium alloy (2024, 1070, 6060 and 5754) were used. The initial AlN powders were characterized by scanning electron microscopy. The composites were studied by light microscopy, scanning and transmission electron microscopies and energy-dispersive X-ray spectroscopy. Particle-matrix interfaces were observed using high-resolution electron microscopy. As a result of the melt infiltration process, the composites are very dense and the microstructure shows a homogeneous distribution of the reinforcement. The interfaces are clean with very little porosity. Some Al2Cu precipitates were observed in the 2024 matrix.

The effect of 12‐O‐tetradecanoylphorbol‐13‐acetate on Sertoli cell morphology and cytoskeletal organization: an in vitro study by means of cryo‐SEM and fluorescent techniques

“…Thus, the in vitro changes of cytoskeletal organization on immature Sertoli cells after the application of TPA could reflect analogous alterations in the physiological morphogenesis and function of the seminiferous tubules of the adult testes. During the past decade, SEM has been increasingly used in material sciences (Chedru et al, 1999;Denry et al, 1999;Severini et al, 1999;Sternitzke et al, 1999) as well as in biomedical applications (Mironov and Mironov, 1985;Mitsushima and Katsumoto 1990;Gallego et al, 1997;Wang et al, 1997;Okanue et al, 1998;Wang et al, 1998;O'Donell et al, 1999;Sakamoto et al, 1999). In the present work the cells were observed at a frozen hydrated state in a SEM equipped with a cold stage at -185°C.…”

Transmission electron microscopy studies of squeeze cast Al–AlN composites

“…These routes as well as our process lead to a high volume fraction of AlN (40–65 vol.%) (Lai & Chung, 1994; Couturier et al ., 1997.). The maximum volume fraction obtained with our process is about ∼50 vol% AlN (Chédru et al ., 1999). A high volume fraction of reinforcement is essential to fit the thermal properties required for such a composite in the electronic field (heat sinks, packaging, etc.).…”

“…A detailed analysis of discs (diameter: 205 mm) fabricated by the infiltration method described above and containing the AlN composite part (100 × 100 × 3 mm 3 ) in the centre surrounded by an excess of Al has been already published (Chédru et al ., 1999). Composites up to 3 cm in thickness could have been fabricated after optimization of the process.…”

“…The pressure was applied immediately with a maximum of 130 MPa. The whole infiltration cycle does not take more than 120 s. A detailed description of the process has already been published (Chédru, 1999; Chédru et al ., 1999).…”

Melt Infiltration Casting of Alumina Silicon Carbide and Boron Carbide Reinforced Aluminum Matrix Composites

“…Melt infiltration with and without pressure techniques are not always succesful for all combinations, Since aluminum alloy surface tension is a strong function of surface active elements and Mg content of the alloy, wetting and liquid penetration is improved by high pressure application on top of liquid aluminum during squeeze casting [12].…”