Trans. Nonferrous Met. Soc. China 25(2015) 1011−1019 Interaction between AE44 magnesium alloy and SiC−Al 2 O 3 −SiO 2 ceramic foam Matej STEINACHER 1 , Primož MRVAR 2 , Franc ZUPANIČ 1 1. Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, SI-2000 Maribor, Slovenia; 2. Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva cesta 12, SI-1000 Ljubljana, Slovenia Received 5 May 2014; accepted 8 October 2014 Abstract: The interaction between a molten magnesium alloy AE44 and a SiC−Al 2 O 3 −SiO 2 ceramics and the resulting reaction products were studied. The samples were investigated using optical and electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. SiO 2 was predominantly reduced by Mg during the contact of the magnesium-rich melt with the ceramics. The main reaction product was MgO, whilst Si dissolved in the melt. Two novel tetragonal phases formed at the interface: AlSiRE and AlMgSiRE, having a specific mutual crystallographic orientation relationship. The interactions resulted in strongly connected interfaces between the metal and ceramics after short interaction time; however, interactions lead to disintegration of the ceramics after longer contact time. Key words: metal matrix composites; AE44 Mg alloy; ceramics; interfacial reaction 1 Introduction Metal-matrix composites (MMCs) show improved performances over their matrix alloys. Magnesium matrix composites can offer potential applications within the automobile and aircraft industries. Interpenetrating phase composites (IPCs) usually display superior mechanical properties compared to conventional MMCs reinforced with particles, intermetallic phases, ceramics, and carbon fibres. A unique combination of cellular ceramic materials, with high mechanical strengths and stiffness at low fractional densities, and the ductility of the metallic phase may be considered as a major advantage of metal/ceramic IPCs [1]. They can be produced in various ways [2,3]. The infiltration can be achieved by spontaneous infiltration phenomenon [4−6], gas pressure-assisted infiltration [7,8], or squeeze-casting into a cellular ceramic preform [1,9,10]. Interface behaviour between the matrix and the reinforcement can profoundly affect the properties of the MMCs [11]. The reinforcement type, alloying element, solidification condition, and heat-treatment of MMCs can affect the local chemical composition and the extent of the interfacial reactions of the MMCs [12]. ZESCHKY et al [1,9,10] investigated these IPCs, using ceramic foam as a reinforcing phase. The MgO and Mg 2 Si interfacial reaction products were present at the interface between AZ91 alloy and oxidized SiC−SiO 2 − C−Si ceramic foam, whilst very small amounts of MgO were found in the strut’s centres. Also, Mg 2 Si, MgO, and Al 12 Mg 17 were found in the struts of the ceramic foam (SiO 2 ) infiltrated with AZ31 alloy. MgAl 2 O 4 , Mg 2 Al 4 Si 5 O 18 , and Mg 2 Si were formed at the interface between the AZ31 alloy and SiO 2 −Al 2 O 3 ceramic foam. The interfacial reactions between the Mg-based alloys and ceramic materials have been studied by several researchers (Table 1). BRASZCZYŃSKA et al [13,14] investigated the Mg−3%RE (mass fraction) alloy reinforced with SiC particles. A thick layer was observed at the interface consisting mainly of fine MgO crystals and Ce 3 Si 2 or RE 3 Si 2 particles, whilst at the interfaces between the ZE63 alloy and SiC particles, the CeO 2 and ZrO 2 were formed [15]. HACK et al [16,17], PAGE et al [18], and McMINN et al [19] found the MgO particles at interfaces between the ZE41 alloy and the α-Al 2 O 3 fibres. HU et al [20] reported the presence of reaction products MgO and Al 2 RE within the interface region between the AE44 alloy and the short Al 2 O 3 fibres. This short overview clearly showed that types of the Corresponding author: Matej STEINACHER; E-mail: matej.steinacher@um.si DOI: 10.1016/S1003-6326(15)63692-5