Effect of Quench Delay on Low-Temperature Mechanical Properties of Aluminium Alloy AA2219 Hand Forgings

In aerospace applications, the quench delay (QD) after solution treatment for the alloy AA2219 is to be restricted to 15s. However, extended QDs are also permitted if the job temperature is maintained above 480 degrees C. To understand the effect of QD on low-temperature mechanical properties, AA2219 forgings were water-quenched after solution treatment with QDs of 15, 30, 50, 100, 200 and 300s and their low-temperature tensile properties were evaluated. Metallurgical characterisation using both optical and electron microscopes was performed. The tensile test results indicate that the strength starts decreasing after 200s (corresponds to the temperature 505 degrees C), and the % reduction in the area of cross section is drastically reduced from 25 to 12%. This is a vital input in deciding on the acceptability of forgings having longer QD as AA2219 being a choice of material for cryogenic applications.