Microstructures evolution of nano TiB2/7050Al composite during homogenization

The microstructures evolution of nano TiB2/7050Al composite during homogenization was studied by in-situ scanning electronic microscopy, transmission electron microscope, energy dispersive spectrometer, electron backscattered diffraction and differential scanning calorimeter. The results showed that many secondary phases (SPs) and TiB2 particles coexisted at grain boundaries (GBs). These SPs mainly consisted of S(Al2CuMg) phase and T(Mg(Zn, Cu, Al)(2)) phase. During homogenization, a transformation from T to S phase occurred, and the homogenization was hindered. Furthermore, the strip-type arrangement of TiB2 at Type-I GBs should accelerate homogenization. Comparably, the shell-type arrangement of TiB2 at Type-II GBs can decelerate homogenization, since the aggregated SPs were hard to be dissolved herein. To clarify the effects of the phase transformation and particles arrangement on the homogenization, a modified diffusion model was proposed. Besides, the Vickers hardness increased and the electronic conductivity decreased with the elevated homogenization temperature and prolonged holding duration. Therefore, a multiple-stage homogenization process should be reasonable for nano TiB2/7050 Al composite.