1. Fatigue Crack Growth Behavior of Al-4.5Mg-0.6Sc-0.3Zr Alloy Processed by Laser Powder Bed Fusion
- Author
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Tianping Zhu, Zhan Chen, S. Singamneni, Teresa Guraya, and P. Chernyshova
- Subjects
Equiaxed crystals ,Materials science ,Mechanical Engineering ,Alloy ,chemistry.chemical_element ,Fractography ,Paris' law ,engineering.material ,Microstructure ,Tortuosity ,chemistry ,Mechanics of Materials ,Aluminium ,Metallography ,engineering ,General Materials Science ,Composite material - Abstract
Fatigue crack growth (FCG) behavior of the bimodal (equiaxed and columnar) grain microstructure of Scalmalloy, which is a printable and high strength aluminum alloy, processed by laser powder bed fusion (LPBF) has been studied. Experimentally, FCG tests have been conducted using FCG samples with crack growth direction normal, parallel or 45° to build direction. Tested sample conditions include LPBF with room temperature base plate or heated base plate and as built state or heat-treated state. It has been found that the fatigue crack propagation threshold (ΔKth) values vary insignificantly and are 1.3-1.4 MPa m1/2 for all samples. Metallography examination of samples has shown that the crack path is highly smooth in the sub-micron grain-size equiaxed grain regions and is also generally smooth in the columnar grain regions with zigzag magnitudes no more than 2 μm. Fractography examination has also confirmed the lack of tortuosity in crack path. It is suggested that the small grain nature after LPBF provides little roughness-induced closure mechanism, resulting in low ΔKth values. In Paris region, m = 2.9-3.0 and C = (3-5) × 10-10MPa m1/2, in agreement with the values found in most aluminum alloys.
- Published
- 2021