The metal-matrix composite materials (MMC) consist of 10, 15 and 20 vol 9% of alumina particles (Al2O3p) in a 6061-T6 aluminium alloy matrix. Specimens were taken from hot-extruded rods and low-cycle fatigue (LCF) tests were carried out at various temperatures and strain amplitudes. The fracture surfaces were studied with a scanning electron microscope in order to understand the fracture mechanism of these composite materials under LCF conditions. From the results, it can be concluded that there is a little cyclic softening at lower strain amplitudes, irrespective of the test temperature, except for the 20 vol % MMC at 300-degrees-C. However, at high strain amplitude, the MMCs show cyclic hardening. The LCF behaviour of Al2O3p/6061-T6 is poorer than that of the unreinforced 6061-T6 Al alloy, especially in the short-life, high-amplitude region.
