Fig. 1. Morphologies of cavitation bubbles among dendritic crystals at different moments. (a) 0 ms; (b) 4.750 ms; (c) 4.900 ms; (d) 4.975 ms; (e) 78.800 ms; (f) 162.725 ms; (g) 455.100 ms; (h) 841.000 ms

Fig. 2. Convection under surface tension and acoustic flow under ultrasonic vibration in molten pool^[20]. (a) Without ultrasonic vibration; (b) with ultrasonic vibration

Fig. 3. Different ways of introducing ultrasonic vibration during moving heat source. (a) Introducing from below; (b) following heat source; (c) introducing from side

Fig. 4. Plasma morphologies of molten pool under different amplitude transformer pressures^[28]. (a) 100 N; (b) 220 N; (c) 430 N

Fig. 5. Cross-sectional morphologies of additive components under different ultrasonic powers and frequencies^[32]

Fig. 6. Flow patterns in cross section of molten metal before and after addition of ultrasonic vibration^[34]. (a) With ultrasonic vibration; (b) without ultrasonic vibration

Fig. 7. Schematic of follow-up ultrasonic equipment and cross-sectional grain sizes of cladding layers under different ultrasonic powers^[36]. (a) 0 W; (b) 1400 W; (c) 1600 W; (d) 1800 W

Fig. 8. Cross-sectional morphologies of weld before and after addition of ultrasonic vibration^[39]. (a) Without ultrasonic vibration; (b) with ultrasonic vibration

Fig. 9. Microscopic morphologies of four-layer coatings with and without ultrasonic vibration^[55]. (a)(c) Without ultrasound vibration; (b)(d) with ultrasound vibration

Fig. 10. Morphology changes of cross section of cladding layer after adding ultrasonic vibration^[56]. (a) Dilution rate is 14.1%; (b) dilution rate is 27.3%; (c) dilution rate is 42.9%

Fig. 11. Distributions of ceramic particles within cladding layer before and after addition of ultrasonic vibration^[59]. (a) Without ultrasonic vibration; (b) with ultrasonic vibration

Fig. 12. Corrosion mechanism at grain boundaries of AlCoCrFeNi corrosion surfaces before and after addition of ultrasonic vibration^[65]. (a)‒(c) Without ultrasonic vibration; (d)‒(f) with ultrasonic vibration

Fig. 13. Grain sizes of additive components before and after addition of high-strength ultrasonic vibration^[79]. (a) Without ultrasonic vibration; (b) with ultrasonic vibration

Fig. 14. Morphologies of additive components under different ultrasonic vibration frequencies^[84]. (a) 0 kHz; (b) 25 kHz; (c) 33 kHz; (d) 41 kHz

Fig. 15. Macroscopic morphologies and microstructures of waste containers fabricated by laser additive manufacturing^[95]. (a) Sampling position; (b)‒(d)without ultrasonic vibration; (e)‒(g) with ultrasonic vibration