Cyclic deformation behavior of in situ aluminum-matrix composites of the system Al-Al₃Ti-TiB₂-Al₂O₃

Aluminum-based composites reinforced with in situ ceramic TiB₂ and Al₂O₃ particulates as well as intermetallic Al₃Ti phase were prepared through reactive hot pressing of powders from the Al-TiO₂-B₂O₃ and Al-TiO₂-B systems. In situ composite derived from the Al-TiO₂-B₂O₃ system exhibited lower yield and tensile strengths but higher tensile ductility due to its lower Al₃Ti content. The low cycle fatigue behavior of in situ composites prepared from such systems under total strain-controlled conditions at room temperature was investigated. At low strain amplitudes, stable cyclic response was observed in the in situ composites fabricated from the Al-TiO₂-B₂O₃ and Al-TiO₂-B systems. However, initial cyclic hardening followed by softening occurred in the composite prepared from Al-TiO₂-B₂O₃ system. The fatigue damage was observed to initiate in brittle Al₃Ti blocks. Thus composite fabricated from Al-TiO₂-B₂O₃ system had longer fatigue lives. The fatigue life data of in situ composites can be described by the Coffin-Manson relationship.