The ultrasonic-assisted brazing process was studied both numerically and experimentally. The ultrasonic brazing system was modeled by considering the actual brazing conditions. The numerical model showed the distribution of acoustic pressure within the filler and its variations according to the gap distance at different brazing temperatures. In the experimental part, brazing joints were studied and evaluated under multiple conditions and parameters. Although either the initial compression load or the ultrasonic vibration (USV) can initiate the interaction at the interface, the combined effect of both helped to produce joints of a higher quality with a relatively short brazing time, which can be further optimized in terms of their mechanical strength. The effect of the Si content on the joint interface, and the effect of the brazing conditions on the microstructures were studied and discussed.

Brazing of titanium using low melting temperature filler alloys is a preferred choice regarding cost and preserving its mechanical properties. However, brazing titanium at low temperature is still a challenge, especially regarding aluminum-based filler alloys. During the last years, several brazing methods and Al-based fillers were developed to meet industrial requirements; some of them might achieve some of those requirements. e use of ultrasound in brazing has gained increased attention recently, which helps to reduce the time and the necessity for a special brazing environment, subsequently, reducing cost and increasing applicability. Brazing titanium below the α↔β transformation temperature, using commercial and experimental Al-based fillers of different compositions, is presented in this review; including the procedures of traditional and ultrasound-assisted brazing methods. Correspondingly, the effects of brazing conditions and alloying elements on the mechanical properties and the intermetallic compounds formation are examined.

In this study, ultrasonic vibration (USV) was evaluated in preparation of Al–8wt.%Cu alloys at a lab-scale. Moreover, the role of Ti–6Al–4V sonotrode erosion and its contribution in grain refining were analyzed. Based on the experimental conditions/parameters, it was found that the amount of impurities and the associated porosity were significantly reduced in USV treated alloys. Furthermore, USV reduced the time needed for dissolving the alloying element Cu, nevertheless, the best dissolving of Cu in this study was not possible without introducing further holding time. As a result of using a titanium-based sonotrode, a noticeable content of Ti was found in the ultrasonically treated alloys due to sonotrode erosion under USV. The dispersion of TiAl3 promoted, as a main factor, a grain refining effect at relatively constant and high melt temperature, other possible mechanisms of grain refining have been discussed.

Brazing joints of Ti/Ti under ultrasonic vibration (USV) and compression load were investigated using optimized and modified filler alloys of Al-Si-Cu-(Ni)-(Sr) group prepared in the lab. Preliminary trails at semisolid to liquid states were conducted using the ready Al-Si-Cu-(Mg) alloy as a filler, then the brazing cycle was redesigned and enhanced according to the microstructural observations of the produced joints. USV assisted brazing at semisolid state of low solid fraction was able to produce joints with round silicon morphology and granular , while at high solid fraction, USV was only able to affect the silicon and intermetallic particles. Applying a compression load after ultrasonic vibration, at a designed solid fraction, was proved to be a successful technique for improving the quality of the joints by reducing the porosity, enhancing the soundness of the joint, and the diffusion at the interface. Based on alloy composition and the improved brazing cycle, joints of thin intermetallic layer and high shear strength (of 93 MPa average value) were achieved. The microstructures and the mechanical behavior were discussed based on the filler compositions and brazing parameters.