Alternations of hardness and tensile properties of the ultrasound-assisted aging treatments on the Al-Mg-Si alloy

Abstract

Lightweight metals with appropriate strength are crucial materials among the critical future technologies and sustainable issues. The Al-Mg-Si alloys, which are processed by aging treatments, are considered promising candidates. Hence, the pseudo-binary Al-Mg2Si alloy with an excess Si addition was chosen in this study. In addition, to further manipulate the alloys, besides to the often-controlled two factors of aging temperature and aging time, ultrasound was introduced into the aging system as an additional third factor to further control the aging behaviors. One-step and two-step aging treatments were both conducted to verify the effect of the introduction of ultrasound. It was found that certain alternations of mechanical properties, such as micro Vickers hardness, which is a surface property, were obviously imposed. On the other hand, the tensile strength and fracture strain, which are bulk mechanical properties, showed limited changes between the ultrasound-applied and ultrasound-free specimens. Many possibilities have been proposed and discussed for the observed phenomenon. The cavitation would be the greatest factor in the alternation of the micro Vickers hardness. Microstructures observed by bright-field images were in good accordance with that of the observed mechanical properties.