Influences of the Welding Heat Input and the Repeated Repair Welding on Ti-3Al-2.5V Titanium Alloy

doi:10.1007/s40195-015-0248-2

Abstract

Abstract:

The primary purpose of this study was to determine the effects of gas tungsten arc welding heat input on the high-temperature tensile properties, toughness, and microstructural features of titanium alloy Ti-3Al-2.5V. The secondary objective was to examine the effect of the repeated repair welding on the properties of the alloy. It was also found that the mechanical properties progressively decreased with increasing the repair welding cycles, especially in the case of the weldment after the first welding repair. It was observed that the sizes of the acicular α′ and prior β grain boundaries as well as the volume fraction of the acicular α′ phases increased with increasing the welding heat input. In addition, the amount and size of the acicular α′ phases were found to increase with increasing the repair welding cycles.

Key words: Ti-3Al-2.5V, Repair, welding, Heat, input, Tensile, properties, Microstructure

Hui-Jun Yi, Yong-Jun Lee, Kwang-O Lee. Influences of the Welding Heat Input and the Repeated Repair Welding on Ti-3Al-2.5V Titanium Alloy[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(6): 684-691.

Figures/Tables 18

Table 1 Chemical compositions of base metal and filler metal (wt%)

Identification	C	Fe	Al	V	N	O	H	Ti
Base metal	0.019	0.074	3.07	2.43	0.015	0.10	0.005	Bal.
Filler metal	0.02	0.01	2.98	2.48	0.01	0.10	0.001	Bal.

Fig. 1 Illustration of the welding device

Table 2 Welding and repair welding parameters

Identification	Ampere (A)	Voltage (V)	Welding speed (CPM)	Heat input (kJ/cm)
H01	135.0	13.6	20	8.8
H02	145.0	14.0	20	9.8
H03	155.0	14.1	20	10.6
H04	165.0	14.4	20	11.4
H05	175.0	14.7	20	12.4

Table 3 Welding and repair welding parameters

Identification		Ampere (A)	Voltage (V)	Welding speed (CPM)
Original welding	R0	150.0	15.0	20
1st repair welding	R1	150.0	15.0	20
2nd repair welding	R2	150.0	15.0	20
3rd repair welding	R3	150.0	15.0	20
4th repair welding	R4	150.0	15.0	20
5th repair welding	R5	150.0	15.0	20

Fig. 2 Effect of welding heat input on ultimate tensile strength at ambient temperature

Fig. 3 Effect of welding heat input on ultimate tensile strength at 300 °C temperature

Fig. 4 Effect of welding heat input on ultimate tensile strength at 500 °C temperature

Fig. 5 Charpy impact test results with various welding heat input condition

Fig. 6 Notch strength ratio (NSR) results with various welding heat input condition

Fig. 7 Hardness distribution as per heat input condition

Fig. 8 Effect of repeated repair welding on ultimate tensile strength

Fig. 9 Effect of repeated repair welding on notch tensile strength

Fig. 10 Effect of repeated repair welding on NSR

Fig. 11 Microstructures of weld metal on various welding heat input energy: a weld metal, H01; b weld metal, H02; c weld metal, H03; d weld metal, H04; e weld metal, H05. The yellow arrows indicate acicular α′ precipitate in β grains and the red arrows indicate prior β grain boundaries

Fig. 12 Microstructures of heat-affected zone on various welding heat input energy: a HAZ, H01; b HAZ, H02; c HAZ, H03; d HAZ, H04; e HAZ, H05. The yellow arrows indicate acicular α′ precipitate in β grains and the red arrows indicate prior β grain boundaries

Fig. 13 Weld metal microstructures of repeated repair welding: a 1st repair weld metal (R1), b 2nd repair weld metal (R2), c 3rd repair weld metal (R3), d 4th repair weld metal (R4), e 5th repair weld metal (R5). The yellow arrows indicate acicular α′ precipitate in β grains and the red arrows indicate prior β grain boundaries

Fig. 14 HAZ microstructures of repeated repair welding: a 1st repair H.A.Z (R1), b 2nd repair H.A.Z (R2), c 3rd repair H.A.Z (R3), d 4th repair H.A.Z (R4), e 5th repair H.A.Z (R5). The yellow arrows indicate acicular α′ precipitate in β grains and the red arrows indicate prior β grain boundaries

Fig. 15 SEM images of HAZ microstructures of repeated repair welding: a 1st H.A.Z (R1), b 2nd H.A.Z, c 3rd H.A.Z, d 4th H.A.Z, e 5th H.A.Z. The yellow arrows indicate acicular α′

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