On the variability in static and cyclic mechanical properties of
extruded 7075-T6 aluminum alloy
Abstract
The present paper investigates the variability in the static and cyclic
properties of two nominally identical supplies of the aeronautical Al
grade 7075-T6. Samples were extracted from extruded bars of 15 mm and 60
mm diameter and with slightly different chemical composition. Noticeable
differences were found in tensile strength, total elongation, low- and
high-cycle fatigue strength, despite the nearly identical hardness
value. The diverse mechanical behavior has been imputed to different
extrusion ratio and therefore work hardening along with a more or less
fine distribution of precipitates and dispersoids. The high-cycle
fatigue strength was found to be in direct correlation with the
monotonic yield strength and the size of the largest intermetallic
precipitate. A simple equation based on Murakami sqrt(area) parameter is
proposed to predict the fatigue endurance. Tensile tests and
microstructural analyses are recommended instead of conventional
hardness tests to have a tighter quality control on the mechanical
properties of semifinished products.