Microstructure and Creep Properties of In situ ZrB2/AA6016 Composites Assisted by Ultrasonic treatment

High-energy ultrasonic controlling Al-KBF4-K2ZrF6 reaction system was used to prepare ZrB2/AA6016 nanoparticle-reinforced aluminum matrix composites (PRAMC). Microstructural observations revealed that acoustic fluidic cavitation promoted the collapse and dispersion of nano-clusters. The plateau of the hardening curve indicates that ultrasonic treatment can improve the plasticity and toughness of the composite. Under 250 °C-70MPa, the apparent stress exponents of the matrix alloy, 3wt% ZrB2/AA6016 and 3wt% ultrasonic-assisted ZrB2/AA6016 composites are 7.34, 9.37, 12.62, respectively. The apparent activation energies are 165.20kJ/mol, 178.83kJ/mol and 215.33kJ/mol, respectively. According to the linear correlation coefficient, the true stress index of the composite material is determined to be 5, which indicates that the creep mechanism of the composite material is the dislocation climbing mechanism. Creep fracture analysis showed that the nano-ZrB2 particles can effectively hinder the propagation of cracks, and ultrasonic treatment can effectively alleviate the stress concentration defects caused by nano-clusters.