Vol.:(0123456789) 1 3 Metals and Materials International https://doi.org/10.1007/s12540-019-00557-z Infuence of Thermomechanical Treatments on the Microstructure and Mechanical Properties of Aluminium Alloy AA2219 Hand Forgings M. Arumugam 1  · P. Ramesh Narayanan 2  · V. Muthupandi 3 Received: 23 August 2019 / Accepted: 20 November 2019 © The Korean Institute of Metals and Materials 2019 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 infuence of cold compression on the extent of benefts obtainable on mechanical properties in forgings. In the present study to identify a thermo-mechanical treatment that can yield the maxi- mum tensile strength, solution treated AA2219 forgings were subjected to cold deformation ranging from 0 to 25% and then artifcially 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 efect 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. Keywords Aluminium alloy AA2219 · Solution treatment · Cold compression · Artifcial ageing · Microstructure · Mechanical properties · Low temperature tensile test 1 Introduction Aluminium alloy AA2219 is one of the most suitable mate- rials for aerospace applications primarily due to its weld- ability characteristics coupled with excellent resistance to stress corrosion [1–4]. This high strength heat treatable alloy is extensively used for aerospace tankage applications as its copper content greater than the solubility limit results in good weld efciency. It consists of about 5.8%–6.8% Cu and small amounts of other alloying elements such as Mn, Ti, Zr and V. Figure 1 shows the portion of aluminium–cop- per binary phase diagram. Temperature ranges for solution annealing, solution treatment, and precipitation heat treat- ment are identifed in the diagram. This alloy is a common choice for cryogenic applications due to its excellent cryo- genic properties. It ofers high strength (YS = 390 MPa, UTS = 470 MPa in diferent aged conditions), and very good resistance to stress corrosion cracking. Due to these facts, AA2219 is an obvious choice for tankages and pressure ves- sels for aerospace applications. High strength is attributed to the precipitation of the Al 2 Cu phase upon solutionising and artifcial aging. Further improvement in strength is achieved by cold working, immediately after solution treatment pre- ceding aging and these conditions are designated as T851/ T852 for forgings and T87 for sheets and plates. As in all heat treatable aluminium alloys, in AA2219 also the maximum strength is obtained by artifcial ageing after solutionising. Residual stresses are developed in the forg- ings during quenching after solutionising. Since thermal * M. Arumugam arumugamm@rocketmail.com 1 Liquid Propulsion Systems Centre, ISRO, Thiruvananthapuram, Kerala 695547, India 2 Vikram Sarabhai Space Centre, ISRO, Thiruvananthapuram, Kerala 695022, India 3 Department of Metallurgical and Materials Engineering, NIT, Tiruchirappalli, Tamil Nadu 6200015, India