Grain Refinement and Mechanical Property Improvements in Ultrasound-Assisted Brazing of SiC_p/Al Composite Materials

The effect of additional ultrasonic treatment (AUT) on grain refinement and distribution of the SiC particles in brazing seam at different temperatures during the solidification process of brazed joints was investigated, and the mechanism model was constructed. The reason for the microstructural changes induced by AUT was explained. The experimental results indicated that the AUT could effectively refine grain, promote element diffusion, and improve the macroscopic uniformity of SiC particles. Further, the effect of AUT was different at different temperatures. At 480 °C, the power ultrasound promoted the SiC particles migration and grain nucleation. In the semi-solid temperature range, the ultrasonic cavitation played a leading role in help α-Al growing to equiaxed grains. In solid-state, ultrasound only played a role in promoting elements diffusion. When the temperature was 420 °C, the ultrasound effect is best that the average grain size of α-Al is 14.6 μm, the joint's shear strength is 196.5 MPa.