Quench Sensitivity of a 7A46 Aluminum Alloy

The quench sensitivity of a 7A46 aluminum alloy is studied by an interrupted quench method. The temperature–time–property (TTP) curves for the electrical conductivity and hardness are determined by measuring the as-quenched electrical conductivity and as-aged hardness, respectively. The TTP curves for the electrical conductivity and hardness all show that the nose temperature is 295°C and that the temperature zone with quench sensitivity and a fast phase transformation ranges from 265°C to 325°C. Transmission electron microscopy (TEM) images show that Al3Zr particles and grain boundaries are preferred nucleation sites for coarse η phases. With the extension of the isothermal holding time at 295°C, the size and density of these coarse η phases increase, resulting in a decreasing density of GP zones and η′ phases after aging treatment, and the precipitate-free zones (PFZ) become wide. To obtain good mechanical properties of the alloy and reduce residual stress, the cooling rate should be controlled at 1°C/s in the quench-sensitive zone and appropriately reduced outside the quench-sensitive zone.