Microstructure, billet surface quality and tensile property of (Al2O3 + Al3Zr)p/Al composites in situ synthesized with electromagnetic field

The aluminum matrix composites reinforced by Al2O3 and Al3Zr particulates were fabricated via in situ chemical reaction between Al–15 wt.% Zr(CO3)2 systems. In the process of in situ reaction, a low frequency electromagnetic field (EMF) is employed to improve the conditions of reaction between reactants powder and melt. The optimized electromagnetic density of low frequency EMF is 0.025 T. During the direct chill casting process of composites melt, the custom-designed electromagnetic fields are introduced to control the microstructures and improve the billet surface quality. XRD analysis shows that Al2O3 and Al3Zr reinforcement phases have been obtained. The Lorenz force improves the kinetic condition and accelerates the nucleation of endogenetic particulates. Microstructure analysis by SEM indicates that the average size of particulates and grain size of matrix are refined to 0.5–1 μm and 20–40 μm, respectively. The surface quality of round billet is greatly improved by the high frequency EMF. The results of tensile properties test show that the tensile strength of composites in situ fabricated with EMF is 254.6 MPa, which is increased by about 104 MPa and 69.4% compared with those of composites in situ fabricated without EMF.

► (Al2O3 + Al3Zr)p/Al composites were fabricated from Al–Zr(CO3)2 systems via direct melt reaction (DMR) method. A low frequency electromagnetic field (EMF) is employed to improve the conditions of reaction between reactants powder and melt. The optimized electromagnetic density of low EMF is 0.025 T.
► In direct chill casting process of composites melt, a custom-designed EMF is introduced. The Lorenz force improves the kinetic condition and accelerates the nucleation of endogenetic particulates. The average size of particulate and grain size of matrix are refined to 0.5–1 μm and 20–40 μm separately.
► The surface quality of round billet is greatly improved by the high frequency EMF. The optimized output current of high frequency EMF is 80 A, the billet has the best surface quality.
► The tensile strength of composites fabricated with EMF is 254.6 MPa, which is improved 69.4% than that of composites fabricated without EMF.