Fig. 1. DED system and schematic for joining. (a) Robot and laser system; (b) powder feeder and ultrasonic vibration system; (c) robot arm; (d) schematic of DED joining; (e) pore changes under ultrasonic vibration assistance

Fig. 2. Al-Mg-Sc-Zr alloy substrate formed by SLM and powder for joining. (a) Al-Mg-Sc-Zr substrate formed by SLM; (b) schematic of slot size; (c) slotted aluminum alloy substrate; (d) Al-Mg-Sc-Zr powder

Fig. 3. Samples joined with different process parameters and size of tensile sample. (a) Sample under energy density of 75 J/mm² and size of tensile sample; (b) sample under energy density of 100 J/mm²; (c) sample under energy density of 125 J/mm²; (d) sample under energy density of 150 J/mm²

Fig. 4. Metallographic structure of samples with and without ultrasonic vibration and hot isostatic pressing. (a) Energy density is 150 J/mm²; (b) energy density is 75 J/mm²; (c) energy density is 100 J/mm²; (d) energy density of 125 J/mm²; (e) ultrasonic current is 0.8 A; (f) ultrasonic current is 1.2 A; (g) ultrasonic current is 1.6 A; (h) sample surface without hot isostatic pressing; (i) sample surface with hot isostatic pressing; (j) metallographic structure without ultrasonic vibration and with hot isostatic pressing; (k) metallographic structure with ultrasonic vibration and with hot isostatic pressing and microhardness curve

Fig. 5. SEM images of pores. (a) Pores distributed around the interface; (b) magnified morphology of the pore

Fig. 6. Efficiency of space filling and microhardness of samples with and without ultrasonic vibration assistance. (a) Efficiency of space filling of samples with and without ultrasonic vibration assistance; (b) microhardness of samples with and without ultrasonic vibration assistance

Fig. 7. Tensile properties and fracture morphologies of specimens with and without ultrasonic vibration assistance. (a) Stress-strain curves; (b) fracture location of different tensile samples; (c) fracture location with 1.6 A current ultrasonic vibration and 150 J/mm² energy density; (d) fracture location with 150 J/mm² energy density and without ultrasonic vibration; (e) fracture morphology with 150 J/mm² energy density and without ultrasonic vibration; (f) magnified fracture morphology with 150 J/mm² energy density and without ultrasonic vibration; (g) fracture morphology with 1.6 A current ultrasonic vibration and 150 J/mm² energy density; (h) magnified fracture morphology with 1.6 A current ultrasonic vibration and 150 J/mm² energy density; (i) stress-strain curves with and without ultrasonic vibration and with hot isostatic pressing; (j) fracture morphology with 1.6 A current ultrasonic vibration and hot isostatic pressing; (k) magnified fracture morphology with 1.6 A current ultrasonic vibration and hot isostatic pressing

Fig. 8. Microstructure and chemical composition distribution in the joining zone of specimens fabricated with and without ultrasonic vibration. (a) Microstructure with 1.6 A current ultrasonic vibration and 150 J/mm² energy density; (b) distribution of strengthening phase with 1.6 A current ultrasonic vibration and 150 J/mm² energy density; (c) element content of strengthening and non-strengthening phase with 1.6 A current ultrasonic vibration and 150 J/mm² energy density; (d) microstructure and element distribution of specimens with 1.6 A current ultrasonic vibration and 150 J/mm² energy density; (e) microstructure and element distribution of specimens with 150 J/mm² energy density and without ultrasonic vibration

Fig. 9. XRD spectra of substrate and joining zone with and without ultrasonic vibration. (a) 30°-80°; (b) 30°-45°