Correlation of Deformation Strain with the Tensile Properties and Fracture Mode of the AA 2014 Alloy Using Simulations and Experiments

Abstract The influence of deformation strain on the tensile properties of the forged bar was studied in the present study. An aerospace structural Al alloy (AA 2014) was selected for the experiments. In order to understand the strain distribution inside the forged bar, the forging process was simulated using the DEFORM3D finite element software. The model was used to predict the stress and temperature distributions. Tensile sample locations were identified based on the deformation strain values predicted by the model. The samples were tested under both notched and unnotched conditions. Variation of tensile properties with the deformation strain was correlated with the microstructure. The fractography of the tensile samples was analyzed with the aid of scanning electron microscopy to identify the failure mode. The important results of the present study are: (1) the strength and ductility properties increase with the increase of deformation strain for both smooth and notched conditions. However, this increase was not correlated to the strain. This uncorrelated variation was attributed to the complex variability in the grain size/structure in the material. (2) Microstructure examination revealed that the variation in the grain size reduced with the increase of deformation strain. The observed grain refinement with the increase of deformation strain was mainly attributed to the strain induced grain fragmentation and dynamic recovery. (3) The fractography of the smooth specimens showed that ductile fracture features, such as dimples and ductile tear regions, were more significant above a strain of 1.34, indicating improved ductility. On the other hand, for the notched specimens, brittle fracture features such as cleavage facets and ridges were predominant for all the strain value conditions. (4) The fracture appeared to be transgranular type in both the smooth and the notched samples for the tested strain range.