Effect of B4C Granulometric Composition on Microstructure and Mechanical Properties of B4C-Al Composites

B4C-Al composites were prepared by infiltrating aluminum into porous B4C preform in vacuum and the effect of B4C particle size fraction on the microstructure and mechanical properties of composites were analyzed. The results showed that B4C-Al composite is mainly composed of B4C, Al, AlB2 and Al3BC. With increasing the fine particle B4C (d(50)=1 mu m) content, the hardness decreases while the bending strength increases gradually, and the fracture toughness increases first and then decreases slightly. The B4C-Al composite with 40 mass % fine particle B4C shows the optimmum mechanical properties. The porosity, hardness HRA, bending strength and fracture toughness of the sample were 1.08 %, 71.7, 505.8 MPa and 6.41 MPa.m(1/2), respectively. It was found that the toughening of the composites is mainly resulted from the addition of ductile aluminum and the increase of fine particle B4C content. The tear ridge and dimple on the fracture surface in the B4C-Al composite increase with increasing the infiltrated aluminum content showing inter/transgranular fracture mode.