Characterization of the microstructure, texture and mechanical properties of 7075 aluminum alloy in early stage of severe plastic deformation

Abstract

The present investigation was conducted to study the microstructural, mechanical and texture evolutions of a 7075 aluminum alloy at the early stage of severe plastic deformation. In this regard, three different techniques were elaborated (for just one pass) to ensure maintaining different deformation modes. These were done applying Multi-Axial Forging (MAF), Accumulative Back Extrusion (ABE) and Friction Stir Processing (FSP) under predetermined thermomechanical condition based on the Zener-Hollomon value. The macrostructures of the deformed materials demonstrate a unique flow pattern and distribution of grain refinement zones, especially in ABE and MAF methods. The EBSD characterization results reveal the presence of accumulated micro-shear bands, which have been ended to an outstanding grain refinement. The results show occurrence of both discontinues and continues dynamic recrystallization (mainly in the stir zone) in the FSPed materials. The mechanical examinations display a significant improvement of both yield and ultimate tensile strength values in all methods. Moreover, the tensile tests were applied in different directions to evaluate the mechanical anisotropy of the deformed materials. The results exhibit higher capability of FSP in delivering more isotropic properties in comparison to the other techniques. In addition, the macro-texture results approve the stronger effect of FSP on fading the initial rolling anisotropy out.