Corrosion Fatigue of Aluminum-Copper-Lithium Alloy 2050-T84 Submitted at Salt Spray and Aqueous Saline Solution

Abstract

Interest in the improvement of the structural performance of aircraft has begun in the substitution of aluminum alloys due to the possibility of reduction of density, an increase of stiffness, high fracture toughness, greater resistance to the propagation of cracks by fatigue and greater resistance to corrosion. In these issues, the aluminum-copper-lithium alloy 2050-T84 is outstanding, which presents excellent mechanical properties even when subjected to aggressive atmospheres. The failure of structural components of aircraft occurs due to several factors that may arise from microstructural defects and/or applied static or cyclic stresses associated with atypical environments such as cryogenic or corrosive. In this sense, the results have evidenced the presence of precipitates that influence in the increase of the mechanical strength, behavior of fracture toughness, fatigue life, and corrosion fatigue, in different temperatures and aggressive means. Tensile and fracture toughness tests at 23 and À60°C the material showed ductility retention without a significant difference in the results. Fatigue crack growth in air and corrosion fatigue with 3.5 and 5% NaCl and aqueous solution with 3.5% NaCl showed a meaning difference in the threshold region; however, for the Paris region at the saline environment, fatigue crack growth (FCG) rates are similar.

Fatigue crack propagation of aeronautic AA7050-T7451 and AA2050-T84 aluminum alloys in air and saline environments

“…FCG tests were performed in an air and saline environment. The aqueous solution tests were carried out in an enclosed chamber as reported in a previous publication [17], using a 3.5 wt% NaCl solution produced with demineralized water and high purity NaCl. Frequencies of 15 Hz (air) and 1 Hz (saline environment -3.5 wt% NaCl), stress ratio R = 0.1, at room temperature were used.…”