'Quench sensitivity' of 7075 aluminium alloy plates

Abstract

7075 aluminium alloy is widely used especially in those applications for which high mechanical performances are required. In the technical literature it is well known that the corrosion resistance and the mechanical properties of this material strongly depend on the cooling rate during quenching. This phenomenon is known as 'quench sensitivity'. The main aim of this paper is to investigate the influence of the cooling rate during quenching of samples taken from plates by varying the parameters of the heat treatment and the rolling direction (L, LT and ST). All the samples were heat treated in laboratory equipment to reach T6, T76 and T73 tempers. The samples were prisms (13 × 13 × 100 mm) and were quenched in water; the cooling rate was imposed by changing the water temperature or changing the polymer amount in a water agitated bath at 20°C. In each of the experimented condition, the cooling rate was measured by a thermocouple placed in the sample. Moreover, a finite element method (FEM) simulation was carried out in order to estimate the heat transfer coefficient during the cooling in all the experimented conditions. Tensile and intergranular corrosion tests were performed to point out the influence of the investigated cooling rates.