Effect of Surface and Subsurface Defects on Fatigue Behavior of AlSi10Mg Alloy Processed by Laser Powder Bed Fusion (L-PBF)
Abstract
:1. Introduction
2. Materials and Methods
2.1. L-PBF Processing
2.2. Microstructure Analysis, Tensile Tests
2.3. Surface Finishing and Surface Characterization
2.4. Fatigue Testing
3. Results
3.1. Microstructure
3.2. Surface Morphology and Subsurface Microstructure
3.3. Tensile and Fatigue Properties
3.4. Fractography
4. Discussion
5. Conclusions
- (1)
- The as-built surfaces of the investigated alloy consisted of a number of protruding geometrical features that could be partially (sand blasting) or fully (vibro-finishing, machining and polishing) removed by the considered surface treatments.
- (2)
- As a result, the average roughness amplitude (Sa) of the treated samples could be reduced down to 8.3 µm for the sand blasted samples and to 2.3 and 0.5 µm for the vibro-finished and the machined and polished samples, respectively.
- (3)
- In sandblasted and in vibro-finished samples the obtained fatigue strength revealed to be strongly affected by the population of existing residual subsurface defects and by the residual stress field. A significant improvement of fatigue strength could be achieved after machining and polishing, which allowed by removal of a 0.5 mm layer of material from surfaces and to obtain the lowest value of surface roughness.
- (4)
- The calculated fatigue limits were 95.0, 152.5, and 194.0 MPa for the vibro-finished, sandblasted, and machined and polished samples, respectively.
- (5)
- Geometrical features such as partially melted particles, spatters, and un-melted powder particles stuck on surface and extending outward from the engineering part profile can be easily removed by proper surface finishing operations. However, residual intrusions left on finished surfaces, even when not significantly depleting the roughness profile, can act as a sharp stress raiser, reducing fatigue strength.
Author Contributions
Funding
Conflicts of Interest
References
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Power (W) | Hatch Distance (mm) | Scan Rate (mm/s) | Layer Thickness (mm) | Platform Temp. (°C) |
---|---|---|---|---|
340 | 0.2 | 1300 | 0.03 | 160 |
Relative Density | Vibro-Finished (VF) | Sandblasted (SB) | Machined and Polished (MP) |
---|---|---|---|
Density (%) | 99.58 ± 0.02 | 99.71 ± 0.01 | 99.71 ± 0.01 |
Surface Condition | Sa (µm) | Sv (µm) | Ssk |
---|---|---|---|
As-Built | 15.4 | 85 | 0.74 |
SB | 8.3 | 40 | −0.13 |
VF | 2.3 | 121 | −7.31 |
MP | 0.5 | 6 | 0.05 |
UTS (N/mm2) | 0.2 YS (N/mm2) | Strain at Fracture (%) |
---|---|---|
412 ± 5.5 | 228 ± 4.1 | 7.0 ± 0.1 |
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Hamidi Nasab, M.; Giussani, A.; Gastaldi, D.; Tirelli, V.; Vedani, M. Effect of Surface and Subsurface Defects on Fatigue Behavior of AlSi10Mg Alloy Processed by Laser Powder Bed Fusion (L-PBF). Metals 2019, 9, 1063. https://doi.org/10.3390/met9101063
Hamidi Nasab M, Giussani A, Gastaldi D, Tirelli V, Vedani M. Effect of Surface and Subsurface Defects on Fatigue Behavior of AlSi10Mg Alloy Processed by Laser Powder Bed Fusion (L-PBF). Metals. 2019; 9(10):1063. https://doi.org/10.3390/met9101063
Chicago/Turabian StyleHamidi Nasab, Milad, Alessandro Giussani, Dario Gastaldi, Valeria Tirelli, and Maurizio Vedani. 2019. "Effect of Surface and Subsurface Defects on Fatigue Behavior of AlSi10Mg Alloy Processed by Laser Powder Bed Fusion (L-PBF)" Metals 9, no. 10: 1063. https://doi.org/10.3390/met9101063