Softening and fatigue fracture of Al-Si-X alloy casts

Ductile manner such as dimple fully covered on fatigue fracture surface of the specimens at 523 K. Softening behavior of eutectic or hyper-eutectic Al-Si-Cu-Mg-(Ni, Fe, Mn) alloy casts has been examined to estimate the influence of heating on their fatigue strength at higher temperature. The hyper-eutectic alloys showed remarkable softening rather than eutectic ones. The softening during heating over 523 K may be related to Al-Cu-Mg-Si precipitation and lowered content of Cu in the matrix.