ECCM16 - 16 TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Seville, Spain, 22-26 June 2014 1 PROCESSING AND CHARACTERIZATION OF B 4 C-SiC/(Al,Si) MULTI- CARBIDES COMPOSITES. B. A. Almeida a,* , A. Ravanan a , M. C. Ferro a , P. M. F. Grave a , H-Y Wu b , M-X Gao b , Y. Pan b , F. J. Oliveira a , A. B. Lopes a and J. M. Vieira a a University of Aveiro, Dep. of Materials Engineering and Ceramics, CICECO - Centre for Research in Ceramics and Composite Materials, Campus Universitário de Santiago PT-3810-193 Aveiro, Portugal b Zhejiang University, Department of Materials Science and Engineering & State Key Laboratory of Silicon Materials CN-310027 Hangzhou, P.R. China *brunoalmeida@ua.pt Keywords: B 4 C, composites, mechanical properties, EBSD. Abstract: B 4 C-SiC/(Al, Si) multi-carbide composites were obtained by reactive melt infiltration of B 4 C with Al-Si binary alloy for short times. Phases were characterized by X-ray diffraction. The microstructure and spatial distribution of phases was assessed by SEM with EDS and EBSD. The mechanical properties of hardness and indentation fracture toughness were evaluated and compared with similar results recent published works of composites processed for longer times. The value of EBSD analysis to understand the role of interfaces and brittle/ ductile phases in crack growth resistance is further discussed. 1. Introduction The low reliability of the hard, low density ceramics coming from the inherent limited fracture energy may be overcome by forming composites strengthened by stiff fibers or plastically yielding metallic inclusions that operate in the crack bridging zone [1-3]. Among the light weight engineering materials, the B 4 C ceramics and composites have been extensively studied and find use in technology [4]. Poor sintering of B 4 C demanding high temperatures (1700-2200 ºC) coupled to the use applied pressure as in hot-pressing and spark plasma sintering makes processing expensive [5-6]. Reactive infiltration of B 4 C with low density Al-Si alloys was early demonstrated by Frage et al [7] and gave the possibility to prepare B 4 C-based composites at moderate prices [4, 7-11]. The low density, large ductility of aluminum and wide availability at low price, make Al a relevant selection for strengthening the ceramic matrix. However, wetting of B 4 C by molten Al is strongly dependent on temperature, being poor at temperatures below 1000 ºC although it can improve with selective additions of other metals [7, 12]. Precipitation of easy cleaving Al 4 C 3 is harmful for the mechanical strength of theses composites [7, 12] whereas the presence of SiC increases the hardness and elastic modulus of the composites [5, 11, 13]. The spontaneous infiltration of porous B 4 C with Al-Si alloys has been described already [4, 7, 14]. The objective of the work is to minimize infiltration time without compromising mechanical properties and preserving enough Si in the liquid to prevent formation of the brittle Al 4 C 3 phase, the threshold composition being 12.6 wt% Si [15]. EBSD has been applied in the study