Shear strain localization in AA 2219-T8 aluminum alloy at high strain rates

AA 2219 aluminum alloy is characterised by high temperature strength, good weldability and excellent suitability as choice material for several components in defense and aerospace structures. In this paper, the dynamic impact response of cylindrical specimens of AA 2219-T8 alloy was investigated using the split Hopkinson pressure bar while strain evolution during the dynamic deformation was monitored in situ using digital image correlation (DIC) technique. The results of DIC analysis and microstructural evaluation of the impacted specimens indicated occurrence of heterogeneous deformation characterised by intense shear strain localization. The strain localisation became noticeable after 80 s from the start of deformation. Both transformed and deformed shear bands developed in the specimens and they cracked along the transformed bands at high strain rates. Microstructural analysis of the as-received alloy suggested that it consists of two type of dispersed second phase particles: coarse particles which are 10-45 mu m in size and fine precipitates of sizes less than 1 mu m. Intense adiabatic heating and strain localization led to the dissolution of the coarse second phase particles inside the transformed bands while the fine second phase particles survived the heat. The dynamic mechanical response of the alloy and its tendency to form adiabatic shear bands are influenced by the length to diameter ratio of the cylindrical test specimens. (C) 2016 Elsevier B.V. All rights reserved.