Microstructures and properties of in-situ (ZrB₂ + Al₂O₃)_np/AA6111 composites synthesized under magnetic and ultrasonic fields

ZrB₂ and Al₂O₃ nanoparticle-reinforced aluminum matrix composites were successfully prepared by in situ chemical reaction of the Al-Na₂B₄O₇-K₂ZrF₆ system with magnetic field applied in the in situ reaction and ultrasonic field introduced in solidification. The results indicated that the optimized magnetic frequency was 10 Hz, and the ultrasonic power was 1.0 kW. XRD analysis showed that ZrB₂ and Al₂O₃ nanoparticles have been obtained. The smaller clusters were evenly distributed in the matrix. ZrB₂ and Al₂O₃ nanoparticles were dispersed and uniformly distributed. The average size of particles and grain size of (ZrB₂ + Al₂O₃)_np/AA6111 composites were refined to 45 ± 10 nm and 50.4 ± 12 μm, respectively. The maximum Vickers hardness, tensile strength, yield strength and elongation of the composites synthesized under the optimized magnetic and ultrasonic fields were 142.2 HV, 355.4 MPa, 259.4 MPa and 22.4%, which were 1.34, 1.36, 1.35 and 1.33 times higher than that of AA6111 alloy, respectively. (paper)