Effect of chemical milling on low-cycle fatigue behavior of an Al-Mg-Si alloy

The effect of alkaline chemical milling used for dimensionally reducing aluminum-alloy structures is assessed in terms of total fatigue life and crack-initiation mechanisms. Chemically milled Al-Mg-Si specimens exhibited a 50% reduction in average fatigue lives compared to electropolished Al-Mg-Si specimens at comparable peak-applied loads above macroscopic yield. The fatigue-life reduction of the chemically milled specimens is likely associated with early onset of crack initiation due to pit-induced-stress concentrations. Fractographic analyses suggest a transition in the crack-initiation mechanisms from predominantly {111}-slip plane cracking to partly or predominantly pit-induced-stress driven depending on the depth of surface pits. (C) 2012 Elsevier Ltd. All rights reserved.