Microstructure and mechanical properties of aluminum alloy recycled by cast with mechanical vibration

The effect of mechanical vibration on microstructure and mechanical properties of recycled casting aluminum alloy was studied by optical microscopy (OM) and scanning electron microscopy (SEM). The experiment results showed that mechanical vibration could make the bulky dendrite break, and the primary phase α was transformed into isometric crystal and the secondary dendrite arm space of alloy decreased during the process of solidification of recycled cast aluminum alloy without addition of 3%Al-3B.The grain size of recycled aluminum alloy with addition of 3%Al-3B and morphology of β phase (AlSiFe) could be markedly improved through mechanical vibration in the process of solidification with the increase of vibration frequency, the morphology of β phase (AlSiFe) transformed from long needle-like into short rod-like which uniformly distributed in the grain boundary. The increase of mechanical vibration frequency could also strongly improve the mechanical properties of recycled casting aluminum alloy. When the frequency was 40 Hz, vibration was optimal, the grain size significantly decreased from 91 to 63 μm and the secondary dendrite arm space of alloy arrived at minimum, whose ultimate tensile strength and elongation were 171 MPa and 4.74% respectively, the values of tensile strength and elongation of recycled casting aluminum alloy were increased by 9.6% and 34.6% respectively compared with that under vibration frequency of 0 Hz, and the mechanical properties was ultimate.