Low-cycle fatigue behavior of Al-based composites containing in situ TiB₂, Al₂O₃ and Al ₃Ti reinforcements

Aluminum-based composites reinforced with in situ TiB₂ and Al₂O₃ particles were prepared through reactive hot pressing of TiO₂, Al and B powders. Brittle Al₃Ti blocks were also formed in situ when the B/TiO₂ molecular ratio is smaller than 2. The low-cycle fatigue behavior of in situ composites under total strain-controlled conditions at room temperature was investigated. The results showed that the composite reinforced with in situ TiB₂ and Al₂O₃ particles exhibits a relatively stable cyclic response at low total strain amplitudes. At higher total strain amplitudes, cyclic softening from the onset of deformation was observed. However, the presence of Al₃Ti blocks led to a very slight cyclic hardening followed by softening at total strain amplitude of 0.4%. Moreover, the intermetallic Al₃Ti blocks reduced the fatigue life of in situ composites as they promoted microscopic cracking during cyclic deformation. Finally, the fatigue life data of in situ composites can be described by the Coffin-Manson relationship.