Low Cycle Fatigue of A356-T6 Cast Aluminum Alloy

Smooth specimen low cycle fatigue behavior of A356-T6 cast aluminum alloy with secondary dendritic arm spacing (DAS) of 36 and 58 µm was obtained under room temperature test conditions. Under strain-controlled axial fatigue conditions, cyclic strain hardening occurred for both DAS values. Hysteresis loops were skewed from 1 to 13% toward the compression side. At higher strain amplitudes the smaller DAS had slightly better fatigue resistance while at the lower strain amplitudes the fatigue resistance was essentially the same for both DAS values. Many test specimens failed outside the test gage length and were thus considered invalid tests. This large number of invalid tests was attributed to surface and near surface discontinuities. Log-log linear low cycle fatigue properties were obtained but these values should be used with caution due to apparent bi-linear log-log elastic strain-life behavior.