The effects of heat treatment on the microstructure and cyclic behavior of A7N01-T4 aluminum alloy

Multi-level tension-compression tests were carried out on A7N01-T4 samples undergoing a series of non-isothermal heat treatments beforehand. Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were performed to analyze the evolution of precipitations. Thermal cycles have significant influence on its plastic constitutive relation. In an interval of peak temperature from 350 °C to 450 °C, the alloy re-precipitates a large number of non-shearable η′ and η precipitates and mainly presents kinematic hardening characteristic due to the anisotropy induced by Orowan Loop Helped Reverse Bypass (OHRB) mechanism. Strengthening precipitates grow coarser below this interval and decompose into aluminum matrix over this interval, which are in favor of the dislocation shearing and interaction, and lead to an isotropic hardening behavior of the alloy.