Study of new heat treatment parameters for increasing mechanical strength and stress corrosion cracking resistance of 7075 Aluminium alloy

摘要

For many years 7075 Aluminum alloys have been widely used especially in those applications for which high mechanical performances are required. It is well known that the alloy in the T6 condition is characterized by the highest ultimate and yield strengths, but, at the same time, by poor stress corrosion cracking (SCC) resistance. For this reason, in the aeronautic applications, new heat treatments have been introduced to produce T7X conditions, which are characterized by lower mechanical strength, but very good SCC behavior, when compared with the T6condition. The aim of this work is to study the tensile properties and the SCC behavior of 7075 thick plates when submitted to a single step ageing by varying the ageing times. The tests were carried out according to the standards and the data obtained from the SCC tests were analyzed quantitatively by an image analysis software. The results show that, if compared with the T7X conditions, the single step ageing performed in the laboratory can produce acceptable tensile and SCC properties. The data should be confirmed by experiments carried out on thick plates submitted to heat treatments in industrial furnaces.