Low Cycle Fatigue of Precipitation Hardened Aluminum Alloy

Abstract

In this work, the influence of different heat treatments on the mechanical properties and fatigue life under low cycles of wrought 7075 aluminum alloy was experimentally investigated. The heat treatments included peak ageing (T6), over ageing (T73) and annealing (O).The flat fatigue specimens were subjected to constant reverse bending load. The tests were performed at the laboratory environment with a frequency of 23.6 Hz and at a stress ratio (R) of -1.For each temper, strain-life graphs were obtained for specimens with notches in the form of central cylindrical holes made by drilling. The fatigue resistance of specimens with notches was compared to the results for notch-free specimens. It was observed that the presence of a stress raiser, such as a drilled hole, lowers the fatigue life for all tempers. However, the notch sensitivity of the fatigue life was different for each temper. The fatigue crack growth rate of T73 and annealed temper was investigated; the results showed that T73 treated sample exhibits higher crack growth resistance. Paris` equation was derived for each temper.