Influence of reinforcement morphology and matrix strength of metal–matrix composites on the cyclic deformation and fatigue behaviour

The cyclic deformation behaviour of three metal–matrix composites, namely AA6061-T6 reinforced with 20 vol.% alumina particles and short-fibres, respectively, and pure aluminium reinforced with 20 vol.% short-fibres, has been investigated at temperatures between T=−100°C and T=300°C in total strain controlled symmetrical push–pull fatigue tests. The cyclic stress response exhibits initial cyclic hardening, subsequent saturation and cyclic softening, depending on the test parameters for temperatures lower than T=150°C. Initial cyclic hardening is less pronounced with increasing temperature and decreasing applied strain amplitude. Short-fibre reinforced composites — both with alloyed and unalloyed aluminium matrix — harden cyclically more than the particulate-reinforced composite. The comparison of the cyclic with monotonic stress–strain curves indicates that, depending on the testing conditions, both cyclic hardening and cyclic softening can occur.