Effects of the Strengthening Mechanism on Fatigue Properties of Precipitation-Hardened Al Alloy

Abstract

The effects of the strengthening mechanism on the fatigue properties of Al-Mg-Si alloy were investigated. Annealing was conducted to minimize the precipitation-hardening effects on Al-Mg-Si alloy, as it could be the most efficient method to stabilize the precipitates. Severe plastic deformation was adapted to obtain grain-refining and work-hardening effects after the annealing process. To evaluate the change in fatigue properties and to investigate the dominant strengthening mechanisms in the specimens, fatigue crack propagation and low-cycle fatigue tests were performed. The experimental results showed that the fatigue crack propagation rate of the annealed specimen was higher than those of other specimens that were grain-refined and precipitation-hardened. During the low-cycle fatigue test, the annealed specimen exhibited cyclic hardening and saturation behavior, whereas the grain-refined specimen exhibited saturation and softening behavior. The low-cycle fatigue life and characteristics of the hysteresis loops of the specimens were evaluated using various parameters. Precipitation-hardened specimens exhibited higher fatigue strength and ductility coefficients than those under other conditions.