In this study, mechanical and tribological behaviours of composites produced by using pressure infiltration method were investigated. Preforms were prepared by using B4C particles with an average grain size of 45 mu m and a volume rate of 60%. Four different matrixes produced by adding different proportions (0, 1, 2 and 4 wt.%) of Mg to AlSi12 aluminium alloy were melted at 800 degrees C and infiltrated to the preform with a pressure of 8 bars. Results whose microstructure characterisation was conducted by using light optical (LOM) and scanning electron (SEM) microscope were supported with X-ray diffraction (XRD) analyses. With the increasing addition of Mg, hardness values and compressive strength increased. This improvement in mechanical properties improved the wear resistance. While the lowest weight loss was achieved with the addition of 4% Mg in low loads as a result of wear tests, the best wear resistance in high loads was observed in composites produced with the addition of 1% Mg.