Abstract:(ZrB₂+Al₂O₃+Al₃Zr)/A356 composites were synthesized by melt direct reaction from A356−(K₂ZrF₆+KBF₄+Na₂B₄O₇) system. The phase compositions and the microstructures of the as-prepared composites were investigated by XRD, SEM and TEM. The results show that the reinforcements are composed of ZrB₂ and Al₂O₃ ceramic phase particles and Al₃Zr intermetallic particles. The ZrB₂ particulates are easy to join together to form some particle clusters and distribute along the α(Al) grain boundary. The morphologies of the ZrB₂ particulates are in hexagon-shape with the size of about 50 nm. The TEM investigation results of Al₃Zr indicate that Al₃Zr grows in the form of facet with the length-diameter ratio of about 20. The morphologies of Al₂O₃ particles are in rectangular-shape and ellipsoidal-shape, with the size of about 0.1 μm. In addition, the interfaces of the matrix and particles are net and no interfacial outgrowth is observed.

Key words: aluminum matrix composites; melt direct reaction; in situ particle; microstructure