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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]

In this work, porous Si 3 N 4 ceramics were successfully and ultrasonically soldered using Sn9Zn2Al solder through sonocapillary and cavitation. Si 3 N 4 ceramics were first ultrasonically wetted and then soldered. The results show that porous Si 3 N 4 ceramics can be wetted in the air within extreme short time of 10 s under ultrasonic. The capillary filling distance of the solder into the ceramic micro-channels achieves a value of 60 μm within 10 s and increases with prolonged ultrasonic time and high ultrasonic power. The infiltrated solder tightly bonded with the ceramic rod. The shear strength of the joint increases at prolonged ultrasonic time and becomes stable after 60 s. A geometric model is built to analyze the infiltration mechanism of the solder, and the result shows that the acoustic pressure inside the solder can reach 4 MPa, which is much higher than the pressure (0.32–1.4 MPa) needed for the sonocapillary action. The wetting mechanism of the solder to the ceramic is analyzed based on the cavitation bubble dynamics calculation. The high liquid velocity, pressure and temperature caused by the collapse of the cavitation bubble serve as the main factors that wet the ceramic. • Porous Si 3 N 4 ceramics are successfully and ultrasonically wetted and soldered by Sn9Zn2Al solder. • The joint can be obtained at a low temperature of 240 °C and short time of 10 seconds. • The solder infiltrates the ceramic through sonocapillary, and the mechanism is analyzed. • The wetting mechanism of solder to ceramic is studied based on the cavitation bubble dynamics calculation. [ABSTRACT FROM AUTHOR]

AlN ceramic was successfully wetted and then joined with nonactive Sn9Zn eutectic solder assisted by ultrasonication in air. The effect of ultrasonic time on the formation of joint was studied. Results indicated that the defect-free joint can be obtained at an ultrasonic time of 5 s. Two regions, namely, AlN/Sn (s,_s) and AlN/Zn (s,_s), were found in the bonding interface. Zn and O accumulated in the AlN/Sn (s,_s) interface. An amorphous and nanocrystalline layer of ZnO formed in the hard-wet AlN surface. And Zn (s,_s) directly bonded with AlN. The low temperature and fast bonding of the AlN was attributed to the high pressure and temperature caused by cavitation effect. The shear strength of the joint increased from 10.6 MPa to 30.7 MPa when the ultrasonic treatment time increased from 5 s to 150 s. With the prolongation of ultrasonic time, more AlN ceramic particles entered the solder and acted as the reinforcing phase. • AlN ceramic was rapidly wetted with a nonactive solder (Sn9Zn) in 5 s assisted by ultrasonication at 230 °C. • Wetting was realized by an amorphous and nanocrystalline ZnO at AlN/Sn interface, and Zn directly bonded with AlN. • The shear strength of the joint was 30.7 MPa with a short wetting time of 150 s. • The triggering mechanism of acoustic cavitation on wetting was analyzed through finite element simulation and calculation. [ABSTRACT FROM AUTHOR]

• Blocky Mg 2 Sn does not present a connection to the continuous Mg 2 Sn in joints soldered by Sn–16Zn. • Joint strength increases with the addition of Zn in solders because Zn blocks crack propagation. • Al exceeds its ultimate solution in solders and increases with the addition of Zn. Dissimilar Al/Mg alloys were soldered by changing the Zn content in Sn-based solders with the assistance of ultrasonic. Results showed that the Al/Mg intermetallic compounds (IMCs) of Al 3 Mg 2 and Al 12 Mg 17 were avoided, but a new IMC of Mg 2 Sn formed in the joints. Mg 2 Sn was blocky inside the joints and continuous near the Mg side. Blocky Mg 2 Sn did not present a connection to the continuous Mg 2 Sn in joints soldered by Sn–16Zn. The shear strength of the joints increased with the addition of Zn into the solders. The maximum shear strength of 49 MPa was obtained when the Sn–16Zn solder was used. The Al content exceeded its ultimate solution in the solder and increased with increasing Zn. The floating of Al grains was observed in the joints soldered by Sn, Sn–3Zn, and Sn–9Zn because of sound radiation pressure, which was blocked by Zn grains in the joint soldered by Sn–16Zn. [ABSTRACT FROM AUTHOR]

Abstract An ultrasonic-induced capillary action method was used to join porous ceramics for the first time. Results indicated that under ultrasonication, the solder infiltrated the porous ceramics and formed a soldered joint. The solder infiltration distance increased with prolonged ultrasonication time and reached 42 μm at an ultrasonication time of 120 s. Ceramic particles were eroded off and flowed into the joint seam because of the intense cavitation within narrow clearances. A fully penetrated layer formed near the joint seam at 120 s. This joint seam had high strength, so cracks propagated throughout the ceramic substrate during shear tests. Overall, our method was suitable for joining porous and microporous materials. Highlights • Porous ceramics were successfully joined by ultrasonic soldering. • Under ultrasonication, solder infiltrated the porous substrate to form a composite region. • Joint shear strength reached 33 MPa at 120 s, and crack propagated throughout the substrate. [ABSTRACT FROM AUTHOR]

Highlights • The physical process and mechanism of cavitation erosion during ultrasonic-assisted soldering were revealed. • Superior erosion effects were obtained using relatively high ultrasonic power and small channel width. • The incubation stage lasted shorter than 0.5 s at a channel width of 0.2 mm. • The removal of the oxide film mainly depended on the stable cavitation stage. Abstract Using pure Sn as filler metal, this study investigated cavitation erosion effects during ultrasonic-assisted soldering. The physical process and mechanism of cavitation erosion were revealed. Superior erosion effects were observed under long ultrasonic times, small channel widths, and high ultrasonic powers. Different vibration intensities were obtained inside filler pool. Region I, which was located far from the sonotrode, exhibited a stronger vibration intensity and better erosion effect than those of the other regions. The erosion incubation stage was shorted than 0.5 s at the channel width of 0.2 mm. Complete oxide layer removal was obtained at an ultrasonic time of 2 s under this condition. The violent cavitation stage was shorter than the erosion incubation stage, and the removal of the oxide layer mainly depended on the stable cavitation stage. [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]

To prevent the formation of Al/Mg intermetallic compounds (IMCs) of Al 3 Mg 2 and Al 12 Mg 17 , dissimilar Al/Mg were ultrasonic-assisted soldered using Sn-based filler metals. A new IMC of Mg 2 Sn formed in the soldered joints during this process and it was prone to crack at large thickness. The thickness of Mg 2 Sn was reduced to 22 μm at 285 °C when using Sn-3Cu as the filler metal. Cracks were still observed inside the blocky Mg 2 Sn. The thickness of Mg 2 Sn was significantly reduced when using Sn-9Zn as the filler metal. A 17 μm Mg 2 Sn layer without crack was obtained at a temperature of 200 °C, ultrasonic power of Mode I, and ultrasonic time of 2 s. The shear strengths of the joints using Sn-9Zn was much higher than those using Sn-3Cu because of the thinner Mg 2 Sn layer in the former joints. Sn whiskers were prevented by using Sn-9Zn. A cavitation model during ultrasonic assisted soldering was proposed. [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]

Highlights: [•] Vibration characteristics of the aluminum surface subjected to ultrasonic waves are shown. [•] The method to eliminate the presence of the zero-amplitude region on the base metal is proposed. [•] The response of liquid solder to the vibration of the base metal surface is presented. [•] The surface vibration of the base metal/liquid solder and the oxide film removal is correlated. [ABSTRACT FROM AUTHOR]

• The acoustic pressure of the solder was increased by four times when the width of the lap clearance was reduced from 0.8 mm to 0.2 mm. • Higher ultrasonic intensity gave rise of more eroded Al spots and grain refinements in the joint and produced stronger joint. • The rapid ultrasonic soldering process was discussed from the viewpoint of the effect of the collapse of cavitation bubbles. To avoid substrate softness, AA7075 were rapidly soldered using a Sn-9Zn solder at 200 °C under ultrasonication. The effect of acoustic intensity on the microstructure and mechanical properties of the soldered joint was studied. The acoustic intensity inside the solder was improved by decreasing the lap width without increasing the input ultrasonic power. Results showed that the softness of the substrate was almost avoided with minimal hardness decrease. The acoustic intensity increased by four times when the width of the lap clearance was reduced from 0.8 mm to 0.2 mm. Pronounced erosion of the substrate occurred under high acoustic intensity. Thus, the content of Al in the joint seam increased from 3.35% to 10.84% after reducing the lap width from 0.8 mm to 0.2 mm. The joint seam was characterized by interlaced fine/coarse Sn-Zn eutectic. The Sn and Zn grains had average sizes of 2.31 and 0.31 μm in the fine eutectic and 3.03 and 0.41 μm in the coarse eutectic. Increasing the acoustic intensity during soldering can effectively increase joint strength. The maximum shear strength of 65.4 MPa and hardness of 29.5 HV were obtained in the joint soldered at 0.2 mm. The cavitation bubble with a nucleation diameter of 10 μm had a large liquid velocity of 7653 m/s, a temperature over 1800 K, and a pressure of 4 × 1012 Pa during its collapse. [ABSTRACT FROM AUTHOR]

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]

Porous Si 3 N 4 ceramics are widely used materials but very difficult to join. In this work, we successfully ultrasonically soldered porous Si 3 N 4 ceramic rapidly at a low temperature of 230 °C. The wetting and bonding mechanism at the ceramic/solder interface was studied. Results showed that the solder rapidly infiltrated the micro-channels of the ceramic during soldering, and high ultrasonic power contributed the sonocapillary distance. Zn and O acted as the main bonding elements. Bonding was realized by the formation of nanocrystalline and amorphous ZnO x region at the wetting interface. Rapid bonding was achieved due to the high liquid velocity, high temperature, and high pressure caused by the collapse of the cavitation bubbles. [Display omitted] • Porous Si 3 N 4 ceramics are successfully soldered within 10 s at 230 °C with the assistance of ultrasonic. • The solder rapidly infiltrates the ceramics through sonocapillary, the infiltration layer widens at high ultrasonic power. • Nanocrystalline and amorphous ZnO x formed at the wetting interface, and the wetting of solder to Si 3 N 4 is achieved. • The wetting mechanism is explained from the viewpoint of bubble dynamics. [ABSTRACT FROM AUTHOR]