Effect of Silver Addition on Mechanical Properties and Stress Corrosion Cracking in a Predeformed and Overaged 7055 Aluminum Alloy

Abstract

Abstract The effect of silver on mechanical properties and stress corrosion cracking (SCC) resistance in a predeformed and overaged 7055 aluminum alloy was investigated. The treatment consisted of solution treating the specimens and then applying 5 % plastic deformation (compression) before aging. The next operation was aging the specimens at 121°C for 24 hours and overaging them at 175°C for 10 hours. Properties of the alloys were investigated by mechanical testing, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and differential scanning calorimetry. Results show that the ultimate tensile strength (UTS) and yield tensile strength (YTS) for the silver-free alloy were 580 and 520 MPa, respectively, and increased to 594 and 567 MPa after the addition of 0.39 % silver. Moreover, the stress corrosion resistance increased ≥ 23 % after adding 0.2 % silver. It can be seen that the addition of silver to predeformed and overaged 7055 aluminum alloy slightly improves the UTS and YTS and increases resistance to SCC significantly. These improvements are due to the interrupting effect of silver on the continuity of magnesium-rich precipitates and the increasing copper absorption in the precipitates.