Effect of ultrasonic field on microstructure and mechanical properties of as-cast 7085 aluminum alloy

Abstract

The effect of an ultrasonic field on the microstructure and mechanical properties of 7085 aluminum alloy during solidification was investigated by optical microscopy, Vickers hardness test, tensile test, scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry, and electron probe micro-analysis (EPMA). The results showed that the grains of aluminum alloy were significantly refined and secondary phases were dispersed and distributed uniformly at the grain boundaries, due to ultrasonic treatment (UST). By EPMA, it was observed that the distribution of the main elements Al, Zn, Mg and Cu was more homogeneous in alloys with UST, than in alloys without UST. The mechanical properties of the aluminum alloy also significantly improved. As demonstrated by the SEM fractography of the fractured faces of several castings, fracture of the unrefined specimens occurred in a brittle manner, whereas the cracks of the refined specimens showed quasi-cleavage fracture.

Keywords

ultrasonic treatment / grain refinement / microstructure / secondary phases

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