Improvement of Formation, Microstructure and Mechanical Properties of TIG Welded TC4 Titanium Alloy by Ultrasonic Coaxial Radiation

doi:10.1007/s40195-024-01766-1

Abstract

Abstract:

In this study, the effects of ultrasonic coaxial assisted TIG welding (U-TIG) on the formation, microstructure, and mechanical properties of TC4 titanium alloy welded joints were investigated. The results indicated that at optimal ultrasonic power and welding current settings, remarkable improvements of welded joint were observed. Specifically, the weld depth-to-width ratio increased by 267% compared to conventional TIG welding, reaching 0.22. Furthermore, the microhardness of the welded seam increased by 53%, reaching 550.1 HV, while the tensile strength of the welded joint rose to 1197.7 MPa, representing a 12.2% enhancement. The compressing effect of ultrasound concentrates the energy of the arc, thereby improving the penetration depth of the welded seam. In addition, ultrasonic cavitation plays a crucial role in refining the grain structure of the weld seam, consequently enhancing its strength.

Key words: TC4 alloy, Ultrasonic coaxial assisted TIG welding (U-TIG), Arc shape, Microstructure, Mechanical properties

Yihao Gao, Boqiao Ren, Yunhao Chen, Xinchen Sui, Xiaohui Zhao, Chenglei Fan, Chao Chen. Improvement of Formation, Microstructure and Mechanical Properties of TIG Welded TC4 Titanium Alloy by Ultrasonic Coaxial Radiation[J]. Acta Metallurgica Sinica (English Letters), 2024, 37(12): 2045-2056.

Figures/Tables 15

Table 1 Chemical composition of TC4 titanium alloy (wt%)

Al	V	Fe	O	C	N	Ti
5.5-6.8	3.5-4.5	≤ 0.30	≤ 0.20	≤ 0.10	≤ 0.05	Balance

Fig. 1 Schematic diagram of welding equipment

Table 2 Experimental parameters

Welding process	Welding current (A)	Ultrasonic power (W)
TIG	100	-
	120	-
	140	-
U-TIG	100	900
	100	1050
	100	1200
	120	900
	140	900

Fig. 2 Schematic diagram: a joint formation, b mechanical properties testing

Fig. 3 Surface formation of weld seams

Fig. 4 Cross-section formation of weld seams: a TIG, 140 A; b 900 W, 140 A; c TIG, 120 A; d 900 W, 120 A; e TIG, 100 A; f 900 W, 100 A; g 1050 W, 100 A; h 1200 W, 100 A

Fig. 5 Depth-to-width ratio of weld seams

Fig. 6 SEM image of the welded seam: a TIG, 100 A; b TIG, 120 A; c TIG, 140 A; d 900 W, 100 A; e 900 W, 120 A; f 900 W, 140 A; g 1050 W, 100 A; h 1200 W, 100 A

Fig. 7 EBSD image of welded seams: a TIG, 100 A; b 900 W, 100 A; c 1050 W, 100 A; d 1200 W, 100 A; e TIG, 100 A, PGR; f 900 W, 100 A, PGR; g 1050 W, 100 A, PGR; h 1200 W, 100 A, PGR

Fig. 8 Tensile strength of welded seams

Fig. 9 Microhardness of WZ and HAZ

Fig. 10 Arc shape of TIG and U-TIG

Fig. 11 Schematic diagram of arc pressure distribution

Fig. 12 Schematic diagram of ultrasound on shield gas

Fig. 13 EDS in the welded seam: a TIG, 100 A; b 900 W, 100 A; c 1050 W, 100 A; d 1200 W, 100 A

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