Strengthening Mechanisms in Al3Zr-Reinforced Aluminum Composite Prepared by Ultrasonic Assisted Casting

Abstract

In the present work, Al3Zr particles were formed in situ by a reaction between hexafluorozirconate (K2ZrF6) and molten aluminum alloy. The aluminum melt with salt addition was ultrasonically stirred to achieve better dispersion of the particles and refine the cast microstructure. Transmission electron microscopy, x-ray diffraction and scanning electron microscopy were used to characterize the in situ composites. The microstructure was refined due to nucleation of uniformly dispersed Al3Zr particles during melting. The dispersion of Al3Zr particles in the aluminum matrix significantly improved hardness, yield strength, ductility and ultimate tensile strength. Theoretical analysis of the strengthening mechanism revealed that thermal mismatch strengthening is the major strengthening mechanism in these composites.