Study on effects of ultrasound on microstructure refinement at semi-solid statement of ultrasonic-assisted brazing SiCp/Al composites

Abstract

Ultrasonic composite brazing uses ultrasonic cavitation and acoustic flow effects to ameliorate the soakage property of SiC particles and brazing material, enabling flux-free brazing of SiCp/Al-MMCs under atmospheric conditions. However, its mechanical properties are limited by the performance of the brazing material, which is often difficult to apply in structures with high strength requirements. In order to break through the limitations of conventional ultrasonic composite brazing of SiCp/Al-MMCs, this paper uses 50 vol.% SiCp/Al MMCs as base material and Zn-16Al brazing material. It applies secondary ultrasound at different times during the solidification of the liquid brazing material to reduce the weld grain size and reinforce the weld intensity by using ultrasonic cavitation and acoustic flow effects. The results show that the addition of secondary ultrasound can reduce the α-Al size and make the SiC particles and α-Al evenly distributed in the joint, which can significantly reinforce the intensity of the weld. The shear performance enhanced with the increase of supersound application second, but too long secondary sonication caused atomization of the brazing material, resulting in unfilled brazing material in the weld, which seriously affected the properties of the weld.