High-cycle fatigue properties of Al-based composites reinforced with in situ TiB2 and Al2O3 particulates

Aluminum-based composites reinforced with in situ TiB2 and Al2O3 particles were synthesized through reactive hot pressing of TiO2, Al and B powders in Al–TiO2–B system, and TiO2, Al and B2O3 powders in Al–TiO2–B2O3 system. Brittle intermetallic Al3Ti phase was also formed in situ and distributed non-uniformly in Al matrices of the composites. The high-cycle fatigue (HCF) resistance of such in situ composites at room temperature was evaluated under fully reversed tension–compression loading. The composites reinforced with large volume content of fined TiB2 and Al2O3 particles exhibited excellent fatigue endurance limit and life under stress-controlled condition. However, intermetallic Al3Ti blocks with a size of several micrometers were detrimental to the HCF resistance of in situ composites reinforced with TiB2 and Al2O3 particles. This is due to the fracture of Al3Ti blocks during cycling, thereby, acting as crack initiation sites.