Fatigue Assessment of Selective Laser Melted Ti-6Al-4V: Influence of Speed Manufacturing and Porosity
Abstract
:1. Introduction and Motivation
2. Materials and Methods
2.1. Material and Geometry
2.2. Manufacturing Conditions
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- Batch 1: Porosity characterization. Fourteen specimens were fabricated with 7 different velocities to evaluate their influence on the porosity (2 samples per velocity): {800, 1100, 1200, 1300, 1500, 1700, 1900} mm/s.
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- Batch 2: Tensile characterization. Two specimens were manufactured with laser velocities of 1200 and 1900 mm/s (1 sample per velocity) for tensile characterization of the material.
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- Batch 3: Fatigue characterization. Fifteen specimens were manufactured with laser velocities of 1200 (7 samples) and 1900 mm/s (8 samples) for fatigue characterization.
2.3. Testing and Characterization Procedures
2.3.1. Porosity Measurement Procedure
2.3.2. Residual Stresses Measurement Procedure
2.3.3. Tensile and Fatigue Characterization Procedure
3. Study of Porosity and Residual Stresses
3.1. Numerical Study: Expected Porosity and Residual Stresses
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- Reference depth (). It ensures that half of the third layer is passed in the material fusion.
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- Ratio depth/width (). It ensures the depth is nearly the same as the width.
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- Ratio length/width (). It ensures the length is not larger than the width.
3.2. Experimental Results
3.2.1. Porosity
3.2.2. Residual Stress Measurement
4. Study of Tensile and Fatigue Behaviour
4.1. Tensile Behaviour
4.2. Fatigue Behaviour
5. Discussion
6. Conclusions
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- The experimental values of the residual stresses increase for lower laser speeds for both maximum and minimum values.
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- The expected porosity was simulated for different laser velocities, establishing limiting energy densities to identify the kind of pores: spherical, sharper or absent.
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- The porosity was qualitatively analysed for seven different velocities, corroborating that, for lower speeds, the pores are spherical while for larger speeds they are sharper and more irregular. On the contrary, for middle velocities no pores were detected.
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- Tensile experimental results at two different laser speeds showed an influence on the mechanical properties of Ti-6Al-4V alloys, especially in the plastic regime.
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- A probabilistic model was used to estimate the fatigue lifetime for two different velocities, concluding that this effect is negligible in comparison with other concurrent variables, such as surface defects or roughness.
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- The influence of speed manufacturing will only be non-negligible when other concurrent effects, such as those caused by the machining process or heat treatments, are softened or relaxed.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Layer Thickness [mm] | Hatch Spacing [mm] | Power [W] |
---|---|---|
0.03 | 0.1 | 200 |
Scan Speed [mm/s] | [mm] | [mm] | [mm] |
---|---|---|---|
800 | 0.115 | 0.447 | 0.157 |
1100 | 0.082 | 0.446 | 0.136 |
1200 | 0.074 | 0.442 | 0.130 |
1300 | 0.067 | 0.439 | 0.125 |
1500 | 0.056 | 0.428 | 0.115 |
1700 | 0.047 | 0.417 | 0.108 |
1900 | 0.039 | 0.400 | 0.101 |
Scan Speed [mm/s] | Energy Density [J/mm] | Porosity [%] |
---|---|---|
800 | 83.33 | 0.00 |
1100 | 60.61 | 0.00 |
1200 | 55.56 | 0.00 |
1300 | 51.28 | 0.00 |
1500 | 44.44 | 0.01 |
1700 | 39.22 | 0.08 |
1900 | 35.09 | 0.36 |
Velocity (mm/s) | (MPa) | (MPa) | (%) |
---|---|---|---|
1200 | 1068.62 | 1158.96 | 6.12 |
1900 | 990.69 | 1114.76 | 6.58 |
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Segurajauregi, U.; Álvarez-Vázquez, A.; Muñiz-Calvente, M.; Urresti, Í.; Naveiras, H. Fatigue Assessment of Selective Laser Melted Ti-6Al-4V: Influence of Speed Manufacturing and Porosity. Metals 2021, 11, 1022. https://doi.org/10.3390/met11071022
Segurajauregi U, Álvarez-Vázquez A, Muñiz-Calvente M, Urresti Í, Naveiras H. Fatigue Assessment of Selective Laser Melted Ti-6Al-4V: Influence of Speed Manufacturing and Porosity. Metals. 2021; 11(7):1022. https://doi.org/10.3390/met11071022
Chicago/Turabian StyleSegurajauregi, Unai, Adrián Álvarez-Vázquez, Miguel Muñiz-Calvente, Íker Urresti, and Haydee Naveiras. 2021. "Fatigue Assessment of Selective Laser Melted Ti-6Al-4V: Influence of Speed Manufacturing and Porosity" Metals 11, no. 7: 1022. https://doi.org/10.3390/met11071022