Strengthening mechanisms in ultrasonically processed aluminium matrix composite with in-situ Al3Ti by salt addition

Al3Ti reinforced Aluminium composites with different weight percent of Al3Ti particles were developed by in situ reaction of aluminium alloy with potassium hexafluorotitanate (K2TiF6). Ultrasonication of the aluminium melt during salt reaction was carried out to refine the cast microstructure and achieve better dispersion of in-situ formed Al3Ti particles. The in-situ composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Al3Ti particles generated in the melt promoted heterogeneous nucleation, which was responsible for grain refinement of the cast microstructure. The well dispersed Al3Ti significantly improved the mechanical properties including ductility, yield strength (YS), ultimate tensile strength (UTS) and hardness. The dominant strengthening mechanism in the composite was the thermal mismatch strengthening followed by Hall-Petch strengthening.