Abstract
In this article, the low cycle fatigue(LCF) behavior of a low silicon
cast aluminum alloy Al-3.5Si-0.5Mg-0.4Cu with T6 treat-state at room
temperature is investigated by extracting samples from aluminum steering
knuckles. Initial microstructure, cyclic stress response behavior and
fatigue fracture are studied. Low cycle fatigue experiment results and
behavior performance of 6 different total strain amplitudes are
included. OM, SEM, XRD and TEM are carried out to observe
pre(post)-fatigue microstructures and fracture. The results demonstrate
that cracks initiate from surface or subsurface defects and higher total
strain amplitude leads to larger sum area of fatigue crack initiation
region and steady crack propagation region, and wider fatigue striation
bandwidth. Furthermore, crack propagates along the interface between
eutectic silicon and α-Al under low strain amplitude while crack grows
through eutectic silicon particle if higher strain amplitude is applied.