Influence of Thermomechanical Treatments on the Microstructure and Mechanical Properties of Aluminium Alloy AA2219 Hand Forgings

Abstract

The heat treatable aluminium alloy AA2219 is subjected to mechanical stress relieving by way of cold deformation after solution treatment to relieve the quenched in stresses as thermal stress relieving is not possible due to the requirement of higher temperature than the ageing temperature. Cold deformation prior to aging has also been found to yield improved strength. Though this phenomenon is to some extent being exploited in aluminium alloy AA2219 sheets and plates, there is no experimental data available to understand the influence of cold compression on the extent of benefits obtainable on mechanical properties in forgings. In the present study to identify a thermo-mechanical treatment that can yield the maximum tensile strength, solution treated AA2219 forgings were subjected to cold deformation ranging from 0 to 25% and then artificially aged. The results indicates that the maximum room temperature tensile strength (both UTS and 0.2% PS) can be obtained at 10% post solution treatment cold deformation. As this alloy is being used for low temperature applications, it is very essential to assess the effect of higher cold compression on the low temperature (77 K) properties and the results show that the 77 K tensile properties more or less same beyond 2% cold deformation. As the weld properties are around 50% of the parent metal properties, any increase in the mechanical properties, is considered to be very crucial and very much needed for this alloy in the absence of aluminium–lithium alloy technology. Hence this study indicate that there is a good scope to increase the amount of cold compression after Solution treatment instead of restricting the same to 2%–5% maximum.