Effect of temperature on the low‑cycle fatigue behaviour of aluminium alloy 64430

A low cycle fatigue (LCF) study of aluminium alloy 64430 was conducted from room temperature to 350°C applying strain amplitudes of ±0.4%, ±0.6% and ±0.8%, at a strain rate of 3 × 10−3 s−1. Tensile behaviour was investigated at room temperature, 80°C and 350°C under displacement control. The alloy features fine Mg- and Si-rich grain boundary precipitates, alongside coarse Fe-, Mn-, and Si-rich intermetallic compounds within the matrix. Under monotonic tension enhanced plastic deformation occurred at 350°C. The cyclic stress response (CSR) decreased with rising temperature; tests from room temperature to 250°C showed initial hardening followed by saturation, whereas at 350°C CSRs were comparable across strain ranges. An anomalous increase in fatigue life with temperature was observed, which is attributed to the soft matrix accommodating more plastic strain. Total hysteresis energy-based models provided the better fatigue-life predictions. Fractography revealed transgranular cracking at high strain amplitudes and mixed transgranular/intergranular cracking at lower amplitudes.