Quench Sensitivity of Aluminum Alloys

The demand of alloys with high strength-to-density ratio is continuously increasing in the engineering world. Beside very expensive materials, such as the titanium alloys and the high strength reinforced polymers, the aluminum alloys represent an excellent alternative to satisfy the challenging requirements of many mechanical and aerospace applications. Among these alloys, the heat treatable grades are much appreciated for the possibility to increase the mechanical resistance significantly after solution treatment and aging. The former aims to create a supersaturated solution that is later modified during the latter by the formation of metastable precipitates involving all or some of the alloying elements. In the technical literature, it is well known that the corrosion resistance and the mechanical properties of these alloys, especially the 7xxx grades, strongly depend on the quenching conditions after the solution treatment. This phenomenon is known as “quench sensitivity.” The main aim of this entry is to discuss the influence of the cooling rate during quenching of different commercial aluminum alloys from mechanical and corrosion points of view. The influence of the rolling direction and of the alloy temper will be considered to focusing the attention on some experimental data obtained on the 7075 aluminum alloy.