In Situ (Al3Zr, ZrB2)/AA6063 Composites Produced by Melt Reaction Technique

The paper presents thermodynamic data for the aluminothermic reaction used to synthesise hybrid composites (Al3Zr, ZrB2)/AA6063. AA6063 alloy was used with K2ZrF6, KBF4 and Na3AlF6 as precursors. Composites containing 2.5, 5, 7.5 and 10% wt.% ZrB2 were produced by direct melt reaction at 900°C and characterised by optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The effect of the salt addition level on the resulting structures is also reported. The compressive behaviour was evaluated at room temperature to an engineering strain of 75% and complemented by tensile tests. The mechanical response is non-monotonic with reinforcement content: the flow stress decreases slightly between 2.5 and 7.5 wt.% ZrB2 and recovers at 10 wt.%, reaching 321.5 MPa at 30% engineering strain against 278.2 MPa for the matrix. The thermodynamic data and microstructural analysis presented here describe the aluminothermic reaction and its effect on the resulting composites.