Research on the Warping and Dross Formation of an Overhang Structure Manufactured by Laser Powder Bed Fusion
Abstract
:1. Introduction
2. Materials and Methods
2.1. Experiment Methods
2.2. Heat Transfer Model
2.3. Stress Model
- The yield deformation process of the material obeys the von Mises yield principle;
- The volume of the material remains when plastic deformation occurs;
- The material follows both the flow rule and the bilinear strengthening rule during the plastic deformation;
- The mechanical properties of the material are in a linear relationship with the stress and strain in a small increment of time;
- The entire powder layer is assumed to melt at once instead of in a track−by−track fashion.
2.4. Physical Description of the Mode
2.5. Material Properties of AlSi10Mg
3. Results and Discussion
3.1. Experiment Result
3.2. Temperature Analysis
3.3. Dross Formation Process
3.4. Deformation Analysis
3.5. Residual Stress Analysis
3.6. Warping Process
4. Conclusions
- The different thermal conductivity between the powder and solid support zone leads to the difference in the molten pool size, which is the main reason for the appearance of dross formation. The simulation result showed that when the laser scanned the powder support zone, the temperature difference between the two regions reached approximately 900 °C, causing the size of molten pool to increase significantly. The molten pool sank due to the actions of gravity and the capillary force, leading to the droplet−like dross formation on the lower surface beyond the designed shape area. With the increase in the number of forming layers, each formed layer plays a role in heat conduction; therefore, the difference becomes smaller and smaller;
- The main reason for warping deformation is that when manufacturing commences, the overhang structure has no constraint; therefore, plastic deformation occurs when the residual stress exceeds the strength of the material. This leads to a low residual stress zone at the edge of overhang area. This deformation affects the subsequent powder spreading process, which makes the warping area exist in a state of remelting. As the number of forming layers increases, the stiffness of the overhang structure increases as well, and the warping deformation gradually decreases;
- In the forming process, the warpage at the top of the parts that can be formed will continue to decrease. The results of the experiment showed that the top warpage reduced to zero for groups 1–6 (2 mm length) with a 1.2 mm (40 layers) height, groups 7–12 (2.5 mm length) with a 1.8 mm (60 layers) height, and groups 13–18 (3 mm length) with a 2.4 mm (80 layers) height. During the simulation process, as the number of forming layers increased, the deformation of the top area decreased from 28.5 μm to 9.18 μm, and the warpage of the parts increased from 2.44 μm to 56.1 μm. These values indicate that with the increase in the number of manufacturing layers, the overall warping of the parts also increased, while the top warping gradually decreased.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Al | Si | Mg | Fe | Mn | Zn | Ni |
---|---|---|---|---|---|---|
Balance | 9.66 | 0.42 | 0.10 | 0.2 | <0.01 | 0.02 |
Trial | Length of Overhang Structure (mm) | Laser Power (W) | Beam Diameter (mm) | Layer Thickness (mm) | Hatch Spacing (mm) | Scan Speed (m/s) | Scan Strategy |
---|---|---|---|---|---|---|---|
1–6 | 2.0 | 300 | 0.1 | 0.03 | 0.13 | 1.3 | 90° rotation |
7–12 | 2.5 | 300 | 0.1 | 0.03 | 0.13 | 1.3 | 90° rotation |
13–18 | 3.0 | 300 | 0.1 | 0.03 | 0.13 | 1.3 | 90° rotation |
19–24 | 3.5 | 300 | 0.1 | 0.03 | 0.13 | 1.3 | 90° rotation |
25–30 | 4.0 | 300 | 0.1 | 0.03 | 0.13 | 1.3 | 90° rotation |
31–36 | 4.5 | 300 | 0.1 | 0.03 | 0.13 | 1.3 | 90° rotation |
37–42 | 5.0 | 300 | 0.1 | 0.03 | 0.13 | 1.3 | 90° rotation |
Temperature (°C) | 20 | 120 | 320 | 520 | 820 | 1120 |
---|---|---|---|---|---|---|
Density (kg/m3) | 2660 | 2643 | 2606 | 2568 | 2374 | 2266 |
Thermal conductivity (W/(m·K)) | 150 | 144 | 130 | 120 | 107 | 63 |
Specific heat capacity (J/(kg·K)) | 700 | 748 | 848 | 1066 | 922 | 925 |
Density (powder) (kg/m3) | 1596 | 1586 | 1563 | 1541 | − | − |
Thermal conductivity (powder) (W/(m·K)) | 1.5 | 1.4 | 1.3 | 1.2 | − | − |
Specific heat capacity (powder) (J/(kg·K)) | 420 | 449 | 509 | 1066 | − | − |
Coefficient of thermal expansion (10−6/K) | 21.7 | 21.8 | 31.4 | 20.6 | − | − |
Young’s modulus (GPa) | 76 | 72 | 64 | 52 | 0 | 0 |
Poisson’s ratio | 0.32 | 0.33 | 0.34 | 0.36 | 0.5 | 0.5 |
Yield strength (MPa) | 250 | 150 | 105 | 70 | − | − |
Latent heat (J/kg) | 3.9 × 105 |
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Lin, P.; Wang, M.; Trofimov, V.A.; Yang, Y.; Song, C. Research on the Warping and Dross Formation of an Overhang Structure Manufactured by Laser Powder Bed Fusion. Appl. Sci. 2023, 13, 3460. https://doi.org/10.3390/app13063460
Lin P, Wang M, Trofimov VA, Yang Y, Song C. Research on the Warping and Dross Formation of an Overhang Structure Manufactured by Laser Powder Bed Fusion. Applied Sciences. 2023; 13(6):3460. https://doi.org/10.3390/app13063460
Chicago/Turabian StyleLin, Pengcheng, Meng Wang, Vyacheslav A. Trofimov, Yongqiang Yang, and Changhui Song. 2023. "Research on the Warping and Dross Formation of an Overhang Structure Manufactured by Laser Powder Bed Fusion" Applied Sciences 13, no. 6: 3460. https://doi.org/10.3390/app13063460
APA StyleLin, P., Wang, M., Trofimov, V. A., Yang, Y., & Song, C. (2023). Research on the Warping and Dross Formation of an Overhang Structure Manufactured by Laser Powder Bed Fusion. Applied Sciences, 13(6), 3460. https://doi.org/10.3390/app13063460