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 degrees C and that the temperature zone with quench sensitivity and a fast phase transformation ranges from 265 degrees C to 325 degrees C. Transmission electron microscopy (TEM) images show that Al3Zr particles and grain boundaries are preferred nucleation sites for coarse eta phases. With the extension of the isothermal holding time at 295 degrees C, the size and density of these coarse eta phases increase, resulting in a decreasing density of GP zones and eta' 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 degrees C/s in the quench-sensitive zone and appropriately reduced outside the quench-sensitive zone.