Effect of TiC nanoparticles on the hot deformation behavior of AA7075 aluminum alloy

Abstract

The hot deformation behaviors of AA7075 aluminum alloy and nano-treated AA7075 aluminum alloy with TiC nanoparticles at 300–450 °C with a strain rate of 0.01–10 s−1 were investigated by isothermal hot compression tests, and constitutive equations and three-dimensional hot processing maps were constructed. The results showed that the hot activation energy of nano-treated AA7075 (190.39 kJ/mol) was larger than that of the AA7075 (174.46 kJ/mol). According to the microstructural observations, the optimal hot deformation windows of AA7075 were 330–400 °C, 0.01–0.1 s−1, 400–450 °C, 0.01–1 s−1, and nano-treated AA7075 was 340–450 °C, 0.01–0.1 s−1. The flow stress of nano-treated AA7075 with TiC nanoparticles was greater than that of the AA7075 at 300 °C and 350 °C, but the difference was insignificant at 400 °C and 450 °C. The hot processing properties of the nano-treated AA7075 deteriorate and the instability region increased significantly, resulting in microvoids, microcracks and sawtooth shear which were the main causes of instability. Lastly, the hot deformed microstructures were analyzed at low and high temperature. During deformation at low temperature, mixed particles of TiC and MgZn2 formed, which pinned dislocations and grain boundary movements. The size of the mixed particles decreased by treating at 400 °C and 450 °C, and the pinning effect was weakened, which limited recrystallized grain growth.