Effects of different initial states on dynamic tensile properties and microstructure of 7075 aluminum alloy

In the present work, the effects of solution quenching (SQ), under-aging (UA), peak-aging (PA), and over-aging (OA) on the dynamic tensile properties of 7075 aluminum alloy have been systematically studied by Hopkinson tensile bar. The results show that the dynamic deformation behavior of the alloy is remarkably affected by the initial aging state. As the aging time increases, the tensile strength of the material first increases and then decreases. Among them, the alloy in the UA state has the highest tensile strength and strain hardening rate. Besides, the evolution of microstructures such as grains, dislocations and precipitation phases has been quantitatively analyzed by electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It has been found that with the increase of aging time, the grain size gradually becomes refined, the density of geometrically necessary dislocations gradually decreases, and the alloy deformation grain distribution is the most uniform in the UA state. Besides, dynamic stretching promotes the growth of precipitated phases, and a large number of fine eta ' phases are distributed in the matrix in the UA state, and the interaction of the fine eta ' phases with the dislocations greatly improves the strain hardening rate and tensile strength of the material.