Laser Welding of BTi-6431S High Temperature Titanium Alloy
Abstract
:1. Introduction
2. Materials and Experiments
3. Appearance of Welded Joints
3.1. Appearance of Welded Joints
3.2. Microstructural Characterization
3.3. Mechanical Properties of the Joints
4. Conclusions
- The base material microstructure of the BTi-6431S high temperature titanium alloy consisted of long strip and equiaxed α phases, with a small amount of β phase distributed between the α phase. The welded region was composed of primary α phase and a significant amount of acicular α’ phase, showing basket weave pattern which resulted from the high degree of supercooling during the laser welding process. The microstructure in heat affected zone contained primary α phase, a small amount of β phase, and acicular α’ phase.
- The microhardness values of the weld zone and heat affected zone were higher than that of base metal. This was due to the fast cooling rate during the laser welding process, resulting in a large amount of α’ martensitic phase distributed in the weld zone and the heat affected zone near the fusion line.
- In this experiment, the tensile strength of the welded joint at room temperature was basically equivalent to the base metal due to the high strength phase distribution and nearly unchanged chemical composition. The tensile strength at high temperature decreased to about 765 MPa which tends to be mainly cleavage fracture with some dimples. The plasticity of the joint was obviously lower than that of the parent metal, and the elongation was about 5%. This was related to the formation of α’ martensite in both the heat affected and fusion zone. All the specimens fractured in the heat affected zone with evidence of necking and it could be observed that the surfaces were oriented at 45° with the tensile axis.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Ti | C | Si | Mo | N | O | Zr | Nb | Sn | W | Al | H | Fe |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Bal. | 0.0077 | <0.1 | 1.26 | 0.0039 | 0.068 | 2.94 | 1.12 | 3.21 | 0.47 | 6.28 | 0.0052 | 0.018 |
Welding Parameters | |
---|---|
Base power (W) | 850 |
Peak power (W) | 1600 |
Pulse duration (ms) | 20 |
Duty ratio (%) | 50 |
Welding speed (mm/min) | 1500 |
Focal length (mm) | 120 |
Focal position (mm) | 0 |
Spot diameter (µm) | 400 |
Mechanical Testing Summary | Sample Reference | Temperature (°C) | UTS (MPa) | YS (MPa) | Elongation (%) | Fracture Location |
---|---|---|---|---|---|---|
Welded specimens | W1 | RT | 1072 | 988 | 5.1 | HAZ |
W2 | RT | 1040 | 1002 | 4.8 | HAZ | |
W3 | RT | 1045 | 991 | 5.0 | HAZ | |
W4 | 650 | 776 | 683 | 4.4 | HAZ | |
W5 | 650 | 755 | 672 | 4.2 | HAZ | |
W6 | 650 | 765 | 681 | 4.5 | HAZ | |
Base material | BM1 | RT | 1060 ± 15 | 982 ± 13 | 16.5 ± 0.3 | - |
BM2 | 650 | 890 ± 17 | 824 ± 16 | 13.2 ± 0.5 | - |
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Zeng, Z.; Oliveira, J.P.; Bu, X.; Yang, M.; Li, R.; Wang, Z. Laser Welding of BTi-6431S High Temperature Titanium Alloy. Metals 2017, 7, 504. https://doi.org/10.3390/met7110504
Zeng Z, Oliveira JP, Bu X, Yang M, Li R, Wang Z. Laser Welding of BTi-6431S High Temperature Titanium Alloy. Metals. 2017; 7(11):504. https://doi.org/10.3390/met7110504
Chicago/Turabian StyleZeng, Zhi, J. P. Oliveira, Xianzheng Bu, Mao Yang, Ruoxi Li, and Zhimin Wang. 2017. "Laser Welding of BTi-6431S High Temperature Titanium Alloy" Metals 7, no. 11: 504. https://doi.org/10.3390/met7110504