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Fatigue is the main cause of mechanical failure in aircraft structures, in which aluminum alloys are employed in approximately 70% of their structural components. Among the microstructural characteristics of aluminum alloys, the hardening precipitates provided by the ageing heat treatment have an important influence in their mechanical properties. In this context, current studies have shown that the two-step ageing heat treatment (T6I4) improves the mechanical properties of 6xxx and 7xxx aluminum alloys. This investigation presents a study of high cycle fatigue behavior of aluminum alloys AA 6351 (T6 and T6I4) and AA 7050 (T7451 and T6I4) as well the influence of microstructural characteristics and two-step ageing heat treatment in the fatigue properties of these alloys. Fatigue tests were performed on smooth and notched specimens.

The objective of this work was to evaluate the creep behavior of the Ti-6Al-4V alloy focusing on the determination of the experimental parameters related to the primary and secondary creep stages. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates. Constant load creep tests were conducted with Ti-6Al-4V alloy in air for coated and uncoated samples and in nitrogen atmosphere for uncoated samples at 500°C to evaluate the oxidation protection on creep of the Ti-6Al-4V alloy. Results indicated the creep resistance of the coated alloy was greater than uncoated in air, but nitrogen atmosphere was more efficient in oxidation protection.