New Al-AlN composites fabricated by squeeze casting: interfacial phenomena

Three Al-AlN composites (2024, 6060, 5754 with similar to45 vol% AlN) fabricated by squeeze casting were studied by TEM. Chemical reactions occurring at the matrix-AlN interfaces have been investigated. MgAl2O4 spinel crystals were found in 6060 and 5754 composites. The magnesium element of the matrix reacts with a very thin alumina layer which is deposited on the AlN surfaces during the liquid infiltration step. The 5754 composites exhibited a stronger reaction leading to the formation of MgO phases with the spinel. Degradation of the mechanical properties was clearly shown in that case. A faceting of the AlN surfaces was observed in all composites. (C) 2002 Elsevier Science Ltd. All rights reserved.