（1.Department of Materials Science and Engineering, North China University of Technology, Beijing 100144, China）（2. School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China）
Four kinds of high volume fraction B4C/Al composites were prepared by pressureless infiltration using four different aluminum alloys (2024Al, 5056Al, 6061Al and 7075Al) and B4C preform with the same particlesize distributions ( 20% 2 μm and 80% 38 μm ), which were named as 2M, 5M, 6M, and 7M, respectively. The effect of matrix alloy composition on the phase composition, microstructure and mechanical properties of the composites was investigated. The results show that all of the composites contain A1, B4C, Al3BC, AlB2, and Fe-Mn-rich phases. Besides, 2M, 5M, and 7M composites also contain the additional phase, AlB10. For all of the composites, the severe interfacial reaction occurred in the aggregation areas of the small B4C particle, with the formation of Al3BC and AlB2. AlB10 is mainly distributed around large B4C particles in 2M, 5M and 7M composites and is integrated with large B4C particles. The Rockwell hardness of the four composites decreased in the sequence 2M (45.7), 7M (43.1), 5M (41.8) and 6M (40.02). The micropores are observed in the 2M, 5M, and 7M composites, resulting in the decrease of the flexural strength and fracture strain of the corresponding composites. Accordingly, 7M composite possesses the lowest flexural strength, being about 296 MPa. Conversely, the flexural strength and fracture strain of the 6M composite are the highest, being about 425 MPa and 0.183%, respectively. This could be mainly attributed to the absence of AlB10 phase and the highest fraction of the residual aluminum matrix in the 6M composite.