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Ultrasonic vibration was applied when soldering carbon fiber-reinforced aluminum composites (C f /Al) in this work. The effects of ultrasonic action time on joint formation, carbon fiber distribution, and mechanical properties of the joints were studied. Results show that, with the assistance of ultrasonic vibration, inactive solder can wet the carbon fiber within dozens of seconds at low temperature (250 °C). Short ultrasonic action time leads to minor erosion of aluminum substrate, thereby restricting the movement of carbon fibers into joint. Extensive erosion of the aluminum occurs with prolonged ultrasonic action time. A uniform distribution of carbon fibers in joint is achieved at 60 s. Wetting of carbon fiber is characterized by amorphous-nanocrystalline oxides on its surface, which can be attributed to the elevated temperature and pressure induced by the cavitation of the solder. Extending ultrasonic time enhances the hardness and the shear strength of the joint. The failure cracks propagate through the substrate when ultrasonic time exceeds 15 s. This work provides referential value when soldering materials with low surface energies. [Display omitted] • Ultrasonic time of 60 s produces a fully carbon fiber reinforced joint. • Carbon fiber is rapidly wetted by inactive SnZn solder under ultrasonication. • Carbon fibers flowing into the joint strengthen the joint seam. [ABSTRACT FROM AUTHOR]

Resistance welding, a favored method for joining thermoplastic composites, often faces the challenge of nonuniform bonding which leads to weak bonding at the overlap edge and compromises joint integrity. This study proposes a novel modification to traditional resistance welding by incorporating ultrasonic during the final stage of the process. We employed various durations of resistance welding and ultrasonic to join the GF/PPS composites, which yielded significant improvements in bonding strength and welding efficiency. Applying ultrasonic introduced a self-adaptive temperature compensation mechanism, enhancing the temperature at the overlap edge while diminishing the temperature difference between the center and edge of the overlap. This method also improved fusion bonding by encouraging resin flow along the unfused interface at the overlap edge, thereby expanding the bonding area. Notably, the introduction of ultrasonic revealed a new bonding mechanism involving the interaction between molten PPS and unmelted PPS, which was thoroughly examined. The results revealed a 19% increase in lap shear strength and a 40% reduction in welding time for joints with ultrasonic compared to those without ultrasonic. [ABSTRACT FROM AUTHOR]

Abstract An ultra-rapid transient liquid phase bonding method was successfully used to join AZ31B Mg alloys by using pure Zn interlayers in air. The bonding time was shortened to 1 s with ultrasonic assistance. Eutectic structures, MgZn, and MgZn 2 formed at relatively low temperatures of 360 °C and 370 °C. Only eutectic structures were observed at a high temperature of 380 °C because the entire joint was filled with eutectic liquid phase at this moment. MgZn 2 had higher hardness and modulus than those of MgZn. The shear strength of joint was inversely proportional to its width. The joint fractured through MgZn 2 at 360 °C and 370 °C, and through eutectoid structures at 380 °C. Graphical abstract Unlabelled Image Highlights • AZ31B Mg alloys were successfully bonded within 1 s with the assistance of ultrasonic. • Joint was formed through liquid phase bonding and diffusion at temperatures lower than 370 °C. • Shear strengths were 31 and 42 MPa when crack propagated through MgZn 2 and Mg Zn eutectic, respectively. [ABSTRACT FROM AUTHOR]

Highlights • Direct observation of cavitation phenomena during ultrasonic-assisted soldering was first recorded. • Numerous tiny transient bubbles dominated in the cavitation field and limited steady bubbles were observed. • Cavitation intensity decreased with ultrasonic time. • Stronger cavitation was observed when small channel width and large ultrasonic power were used. Abstract The cavitation characteristics at filler metal/substrate interface during ultrasonic-assisted soldering were first recorded by high-speed photography in this work. Two kinds of bubbles, steady cavitation bubbles and transient cavitation bubbles were observed. Steady cavitation bubbles did not collapse within one acoustic period and could last longer than 50 acoustic periods. Transient cavitation bubbles formed and collapsed within one acoustic period. The cavitation process was divided into two stages based on the cavitation characteristics. The first violent cavitation stage was in fact the degassing process, which lasted approximately 2700 acoustic periods and was affected by the gas content trapped inside the filler metal and the stronger vibration at the initiation stage of ultrasonic-assisted soldering. The second steady cavitation stage had obvious low bubble density and accounted for the most of the soldering process. Higher cavitation densities were observed when small channel width and large ultrasonic power were used because of larger sound pressures inside the filler metal. [ABSTRACT FROM AUTHOR]

In this work, an ultrasonic-assisted semi-solid brazing method was proposed to join Al/Mg. Oxide films on substrate surfaces can be successfully removed even when filler metal was at semi-solid state. A large quantity of intermetallic compounds (IMCs) formed at 460 °C because of large amount of Al and Mg dissolved into joint caused by strong cavitation. Decreasing the temperature to 430 °C could significantly reduce IMC. However, weak cavitation happened inside low liquid phase fraction at 420 °C, making it difficult to break IMCs and solid phases. [ABSTRACT FROM AUTHOR]

Joint seam is always the weak region of the welded joint. The soldered/brazed ceramic joint always fails through the joint seam due to lower strength of the solder/braze. In this work, to fabricate ceramic joint stronger than its substrate, ultrasonic vibration was used when brazing porous Si 3 N 4 ceramics. Results show that the brazing can be directly realized at 450 °C in air because ultrasonic cavitation can break the oxide layers of braze. Under ultrasonication, high acoustic pressure is obtained in braze, thus it rapidly infiltrates into the porous ceramics. Then, tight bond is realized between the ceramic and braze within several seconds because of the cavitation phenomenon. The transmission electron microscope results show that the main bonding medium at the ceramic/braze interface is an amorphous Al 2 O 3 layer. Shear test reveals that long ultrasonic time is beneficial to the shear strength of the joint. Wetting times longer than 10 s produce joint stronger than the ceramic substrate. This work provides a new insight when joining other porous materials. • Porous Si 3 N 4 ceramics joints stronger than the substrate was fabricated by ultrasonic brazing. • Short ultrasonic time of 10 s and low temperature of 450 °C produce joint stronger than the ceramic substrate. • The wetting interface is characterized by amorphous Al 2 O 3. [ABSTRACT FROM AUTHOR]

We used ultrasonic-assisted transient liquid bonding (UATLP) to join dissimilar Al/Mg alloys with pure Zn interlayer in the air to prevent the formation of Al Mg intermetallic compounds (IMCs). The effects of bonding temperature, ultrasonic power, sonotrode pressure, and interlayer thickness on the microstructure and mechanical properties of the bonded joints were studied. Results showed that the addition of Zn interlayer could effectively depress the Al Mg IMCs. The oxide layer on the Al substrate is incompletely removed at bonding temperature below 380 °C, the Mg side is bonded by eutectic phase, and the Al side is bonded by diffusion. The joint is characterized by Mg Zn eutectic (containing ternary IMCs) and IMCs of MgZn and MgZn 2 layer. MgZn 2 is the weak point of the joint under such a condition, and the joint has shear strength of approximately 20 MPa. The oxide layer on the Al substrate is completely removed when the temperature exceeds 380 °C, the large amount of Al that flows into the joint results in a Mg 32 (Al,Zn) 49 layer adjacent to the Al substrate. The joint gains its maximum strength of 28.4 MPa when thin MgZn 2 and discontinuous Mg 32 (Al,Zn) 49 exist adjacent to the Al substrate. High ultrasonic power, large sonotrode pressure, and thin Zn interlayer could reduce the thickness of MgZn 2. • Al/Mg alloys are bonded through ultrafast ultrasonic-assisted TLP in the air with Zn interlayer to avoid Al Mg IMCs. • IMCs of Al 3 Mg 2 and Al 12 Mg 17 are depressed, and MgZn and MgZn 2 formed when temperature is below 380 °C. • Mg 32 (Al,Zn) 49 , strengthened by nanosize Al particles, formed in joint when temperature is above 380 °C. • The joint gains its maximum strength when thin MgZn 2 and discontinuous Mg 32 (Al,Zn) 49 form adjacent to the Al substrate. • High ultrasonic power, large sonotrode pressure and thin Zn interlayer could reduce the MgZn 2 thickness. [ABSTRACT FROM AUTHOR]

Solidification microstructure of SiC particles reinforced Zn–Al composites under different kinds of ultrasonic exposure was investigated and the origin of the microstructural changes induced by ultrasonic was explained. Under continuous ultrasonic exposure, highly refined and non-dendritic globular matrix structure was achieved but serious particle clustering occurred at the top and peripheral parts of the solidified ingot. Homogeneous particle distribution as well as dramatic grain refinement of matrix metal was observed in the ingot solidified with isothermal ultrasonic processing. Strong supportive evidence showed that acoustically induced dendrite fragmentation was dominantly responsible for the formation of a refined and globular microstructure. The particle clustering was closely related to the pattern of the acoustic streaming and the interactions between the particles with the vessel and the matrix melt. [ABSTRACT FROM AUTHOR]

Brazing is a commonly used method to join porous Si 3 N 4 ceramics; it requires high temperature, long holding time, and vacuum environment. In this work, given the phenomena of sonocapillary and increased cavitation in narrow channels, ultrasonic-assisted soldering was successfully used to join porous Si 3 N 4 ceramics at low temperature of 230 °C in the air within a short period. The effect of ultrasonic time on the microstructure and mechanical properties of the soldered joints was studied. The bonding mechanism of solder to ceramic was studied by scanning electron microscope, electron probe microanalyzer, and transmission electron microscope (TEM). Results showed that the Sn9Zn solder can infiltrate the microchannels of the porous Si 3 N 4 ceramics through sonocapillary within a short ultrasonic time of 3 s. Prolonged ultrasonic time resulted in better wetting of solder to ceramic and wider infiltration layer. The infiltrated solder tightly bonded with the ceramic rod without pores and cracks. The TEM results showed that Zn and O were the main bonding elements. The bonding interface was characterized by nanocrystalline and amorphous ZnO. The shear tests revealed that prolonged ultrasonic time enhanced the joint strength. • Porous Si 3 N 4 ceramics are directly soldered in the air with the assistance of ultrasonic. • Solder is driven by sonocapillary to infiltrate the ceramics, thereby leading to the improvement of the joint strength • The bonding of the solder to ceramic is realized by the formation of nanocrystalline and amorphous ZnO oxide. • Prolonged ultrasonic time results in longer infiltration distance and higher joint strength. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a method of producing uniform particle strengthened bonds between pieces of aluminum metal matrix composite (Al-MMCs), of strength equal to that of the substrate material. SiC particle reinforced Zn-based filler metals were fabricated by mechanical stir casting and ultrasonic treatment, and then used to join pieces of SiCp/A356 composite with the aid of ultrasonic vibration. The filler metals made by mechanical stirring were porous and contained many particle clusters. Ultrasonic vibration was used to disperse the agglomerates and prevent further coagulation of SiC particles during joining, but the method failed to eliminate the porosity, resulting in a highly porous bond. The filler metal treated by ultrasonic vibration was free of defects and produced a non-porous bond strengthened with uniform particles between pieces of SiCp/A356 composite. The presence of surface oxide films at the bonding interface significantly degraded the performance of SiC particle reinforced bond. Removal of this oxide film by at least 4s of ultrasonic vibration significantly increased the bond strength, reaching a value equal to that of the substrate metal. [Copyright &y& Elsevier]

Carbon fiber reinforced aluminum matrix composites (C f /Al) are widely used in various industries. But they are difficult to join because it is hard to realize the wetting and continuity of the carbon fiber in joint. To solve this problem, C f /Al are joined by ultrasonic soldering in this work. Results show that the C f /Al can be wetted within 5 s under ultrasonic. Transmission electron microscope result shows that the surface of the wetted carbon fiber is covered by an amorphous-nanocrystalline layer, which is formed due to the high solder velocity, temperature and pressure caused by cavitation. Carbon fibers flow into the solder after the Al matrix is eroded, guaranteeing its continuity in the joint. Limited carbon fibers flow into the joint at low ultrasonic power of 333.3 W, while a fully carbon fiber reinforced composite joint is obtained at 1000 W. The soldered joints have higher strength than the C f /Al substrate, and its formation mechanism is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Power ultrasonic vibration (20kHz, 6μm) was applied to assist the interaction between a liquid Al–Si alloy and solid Ti–6Al–4V substrate in air. The interaction behaviors, including breakage of the oxide film on the Ti–6Al–4V surface, chemical dissolution of solid Ti–6Al–4V, and interfacial chemical reactions, were investigated. Experimental results showed that numerous 2–20μm diameter-sized pits formed on the Ti–6Al–4V surface. Propagation of ultrasonic waves in the liquid Al–Si alloy resulted in ultrasonic cavitation. When this cavitation occurred at or near the liquid/solid interface, many complex effects were generated at the small zones during the bubble implosion, including micro-jets, hot spots, and acoustic streaming. The breakage behavior of oxide films on the solid Ti–6Al–4V substrate, excessive chemical dissolution of solid Ti–6Al–4V into liquid Al–Si, abnormal interfacial chemical reactions at the interface, and phase transformation between the intermetallic compounds could be wholly ascribed to these ultrasonic effects. An effective bond between Al–Si and Ti–6Al–4V can be produced by ultrasonic-assisted brazing in air. [Copyright &y& Elsevier]