Crack Growth Behavior of AA6082 and AA6061 Aluminum Alloys

Fatigue crack propagation tests have been performed in two heat-treated AlMgSi aluminum alloys under constant amplitude loading and peak overloads. All experiments were performed, in load control using M(T), specimens. Crack closure was monitored in the tests by the compliance technique using a pin microgauge. A strong material dependence effects on the fatigue crack growth were observed. The crack growth behavior of heat-treated aluminum alloys depends mainly on whether the dominant closure mechanism is plasticity-induced or roughness-induced. The enhancement of roughness-induced closure promotes higher crack growth resistance in these alloys. Roughness-induced closure dominates crack closure in 6061-T651 alloy, while in 6082-T6 aged hardened alloy plasticity-induced closure is dominant.