Fracture toughness of in situ TiCp–AlNp/Al composite

The effect of particle size, particle volume fraction, and matrix microstructure on the fracture initiation toughness of in situ TiCp–AlNp/Al composite was examined. The composites were Al matrix reinforced with 7.8–19.6 vol.% of TiC and AlN particles produced in situ by S-V-L reaction synthetics. The average particle diameters of TiC and AlN were 3.5 and 0.9 μm, respectively, which were distributed in the Al in a matrix dispersedly manner. The room-temperature plane-strain toughness measured using three-point bending specimens ranged from 12.7 to 37.5 MPa m. Toughness was adversely affected by an increase in the TiCp–AlNp volume fraction. Fractography revealed that these composites failed in a ductile manner, with voids initiating at the in situ reinforcing TiC and AlN particles. The experimentally measured plane-strain toughness properties of in situ TiCp–AlNp/Al composite agrees with the Rice and Johnson model.