Microstructure Evolution and Mechanical Properties of In Situ TiB2/Al-Zn-Mg-Cu Composites by Electropulsing-Assisted Solution Treatment

The traditional solution treatment is not completely applicable for in situ TiB2/Al-Zn-Mg-Cu composite due to the influence of TiB2 particles. This study investigates the impact of the electropulsing-assisted solution (EAS) process on the microstructure evolution and mechanical properties of TiB2/Al-Zn-Mg-Cu composites. The nonuniform microstructure evolution related to the difference in temperature and current density is supported by simulative and experimental results. EAS treatment significantly enhances the degree of supersaturation, allowing phases surrounding TiB2 particles to dissolve without extensive overburning, unlike traditional solution treatments. This improvement is attributed to the reduced thermodynamic barrier and accelerated atomic diffusion, facilitated by both localized and average Joule heating effects and enhanced thermal electron/phonon scattering. Meanwhile, grain size remains stable during the temperature rise induced by EAS treatment. Furthermore, the mechanical properties of composites increase, among which the increase in strength is mainly ascribed to solid-solution strengthening, and the increase in elongation is related to multiple factors referring to TiB2 particles fracture and interface crack between the undissolved phases and matrix. This study provides an approach to achieve an efficient dissolution of phases aggregated with particles and without widespread overburning in particle-reinforced Al matrix composites via electropulsing techniques.