High cycle fatigue response of in-situ Al-based composites containing TiB₂ and Al₂O₃ submicron particles

Aluminum-based composites reinforced with in situ TiB₂ and Al₂O₃ submicron particles were fabricated via reactive hot pressing of TiO₂, Al, B or B₂ O₃ powders. The high-cycle fatigue (HCF) behavior of such in situ composites at room temperature was investigated under stress-controlled conditions at different load ratios. The S-N curves were determined in fully reversed tension-compression loading. The microstructures and fracture surfaces of in situ composites were examined to reveal their fatigue failure mechanism. The composite prepared from the Al-TiO₂-B system and reinforced with TiB₂ and Al₂O₃ submicron particles exhibited superior fatigue endurance stress and life. However, the composite fabricated from the Al-TiO₂-B₂O₃ system had lower HCF resistance due to the formation of large intermetallic Al₃Ti blocks. The fatigue response characteristics of both in situ composites are discussed in terms of the intrinsic microstructural and extrinsic stress ratio effects.