Effect of Artificial Aging Hardness on Mechanical Properties of AA-2024

日期 : May 2015 - Jan 2016

This study is based on daily experience in the Aerospace Industries. Aircraft structures are mostly made from Aluminum Alloys, especially the 2024 alloy. The high strength of the 2024 alloy is achieved by heat treatment which involve a solution treatment and quenching, after which it is either naturally aged at room temperature or artificially aged above room temperature. In this work, an attempt was made to artificially age the 2024 alloy and examine the effects on mechanical properties and microstructure when introduced at 160°C temperature that is above the normal precipitation treatment temperature (120 °C) for four different ageing times that is for 12hrs, 16hrs, 24hrs and 32hrs after being solution heat treated. The material selected for this study was aluminum 2024 round bar with 25.4 mm (1 inch) diameter purchased from Greysons And Company, Jodia Bazar Karachi. The maximum tensile strength was achieved after 12 hours of aging time. The tensile strength of specimen was equal to that of the usual 2024 T6 strength. The microstructure of the specimen consisted of fine dispersed precipitates of AlCuMg precipitates, and irregularly shaped precipitates of Al2Cu along the grain boundaries. Further increase in aging time tended to decrease the tensile strength due to overaging. The effect on hardness and impact fracture energies were also same. The microstructure of the overaged specimen revealed the formation and coarsening of equilibrium precipitates. Ageing of this material at 160°C temperature showed that strengthening process is successfully done and but aging time to achieve T6 condition was more, as the peak strength was achieved just after 12 hours. Therefore at increased ageing temperature (160°C), the optimum range of aging time to develop full strength is less than 12 hours and further increase in aging time will overage the material. The ability to accelerate this ageing process will be of great benefit to manufactures particularly where time is concerne