Microstructure and Mechanical Properties of a Fiber Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy
Abstract
:1. Introduction
2. Materials and Methods
3. Results and Discussion
3.1. Surface Morphology of Weld Seams
3.2. Microstructure Observations
3.3. Microhardness Measurements
3.4. Tensile Strength
3.4.1. Tensile Strength and Fracture Path
3.4.2. Composition of Grain Boundary Segregation
3.4.3. Morphology of Tensile Fractures
4. Conclusions
- (1)
- Laser welding of an NS Mo alloy under a low heat input resulted in a high aspect ratio of the FZ and uniform widths and depths of FZ over the whole circumference of the joint. In contrast, in the joint prepared with a high heat input, a low aspect ratio of the FZ was observed and both width and depth of FZ increased gradually along the welding direction.
- (2)
- The FZ and HAZ of joint 1 and joint 2 both were softened. The minimum microhardness of the softened zone of both joints was similar and was less than that of BM by about 20%.
- (3)
- When heat input was increased from 250 J/cm to 3600 J/cm, the average grain size of the FZ increased from about 40 μm to about 130 μm, which would significantly reduce the total area of GBs, and therefore might aggravate the segregation of MoO2 at GBs.
- (4)
- The tensile strengths of the welded joints achieved using heat inputs of 250 J/cm and 3600 J/cm were 79% and 35% of that of BM, respectively. Both joints fractured in the FZ and intergranular fracture morphology took up about 30% and 50% of the total area of the fractures of joint 1 and joint 2, respectively.
Author Contributions
Funding
Conflicts of Interest
References
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Sample Number | Laser Power (kW) | Welding Speed (cm/min) | Defocusing Distance (mm) | Heat Input (J/cm) |
---|---|---|---|---|
Joint 1 | 2.5 | 600 | 1 | 250 |
Joint 2 | 1.2 | 20 | 1 | 3600 |
Joint 1 | Joint 2 | |
---|---|---|
Average grain size | 42 μm | 131 μm |
Standard deviation | 15 μm | 40 μm |
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Xie, M.-X.; Li, Y.-X.; Shang, X.-T.; Wang, X.-W.; Pei, J.-Y. Microstructure and Mechanical Properties of a Fiber Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy. Metals 2019, 9, 640. https://doi.org/10.3390/met9060640
Xie M-X, Li Y-X, Shang X-T, Wang X-W, Pei J-Y. Microstructure and Mechanical Properties of a Fiber Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy. Metals. 2019; 9(6):640. https://doi.org/10.3390/met9060640
Chicago/Turabian StyleXie, Miao-Xia, Yan-Xin Li, Xiang-Tao Shang, Xue-Wu Wang, and Jun-Yu Pei. 2019. "Microstructure and Mechanical Properties of a Fiber Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy" Metals 9, no. 6: 640. https://doi.org/10.3390/met9060640
APA StyleXie, M. -X., Li, Y. -X., Shang, X. -T., Wang, X. -W., & Pei, J. -Y. (2019). Microstructure and Mechanical Properties of a Fiber Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy. Metals, 9(6), 640. https://doi.org/10.3390/met9060640