High temperature fatigue of heat treated secondary AlSi7Cu3Mg alloys

The high-temperature fatigue behaviour of a heat treated AlSi7Cu3Mg alloy is reported. Fatigue testing has been performed at room and higher temperatures (473 and 573 K) on specimens previously solubilised at 758 K for 24 h and further aged at 453 K for 8 h. Microstructural and fractographic investigations have been used to quantitatively examine the evolution of strengthening precipitates and the different fracture mechanisms. The results show how the fatigue behaviour is comparable in the temperature range between 293 and 473 K. Then, the fatigue strength decreases by increasing the testing temperature from 473 to 573 K. The uniform distribution of fine strengthening precipitates in the α-Al matrix is affected by higher test temperature, which promotes coarsening phenomena of the precipitates. The failure mode changes from brittle to ductile at 573 K.