Additive manufacturing (AM) as a disruptive technique has offered great potential to design and fabricate many metallic components for aerospace, medical, nuclear, and energy applications where parts have complex geometry. However, a limited number of materials suitable for the AM process is one of the shortcomings of this technique, in particular laser AM of copper (Cu) is challenging due to its high thermal conductivity and optical reflectivity, which requires higher heat input to melt powders. Fabrication of composites using AM is also very challenging and not easily achievable using the current powder bed technologies. Here, the feasibility to fabricate pure copper and copper-carbon nanotube (Cu-CNT) composites was investigated using laser powder bed fusion additive manufacturing (LPBF-AM), and 10 × 10 × 10 mm3 cubes of Cu and Cu-CNTs were made by applying a Design of Experiment (DoE) varying three parameters: laser power, laser speed, and hatch spacing at three levels. For both Cu and Cu-CNT samples, relative density above 90% and 80% were achieved, respectively. Density measurement was carried out three times for each sample, and the error was found to be less than 0.1%. Roughness measurement was performed on a 5 mm length of the sample to obtain statistically significant results. As-built Cu showed average surface roughness (Ra) below 20 µm; however, the surface of AM Cu-CNT samples showed roughness values as large as 1 mm. Due to its porous structure, the as-built Cu showed thermal conductivity of ~108 W/m·K and electrical conductivity of ~20% IACS (International Annealed Copper Standard) at room temperature, ~70% and ~80% lower than those of conventionally fabricated bulk Cu. Thermal conductivity and electrical conductivity were ~85 W/m·K and ~10% IACS for as-built Cu-CNT composites at room temperature. As-built Cu-CNTs showed higher thermal conductivity as compared to as-built Cu at a temperature range from 373 K to 873 K. Because of their large surface area, light weight, and large energy absorbing behavior, porous Cu and Cu-CNT materials can be used in electrodes, catalysts and their carriers, capacitors, heat exchangers, and heat and impact absorption.
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Effects of Build Angle on Additively Manufactured Aluminum Alloy Surface Roughness and Wettability
Abstract Laser powder bed fusion (LPBF) was utilized to create a series of aluminum alloy (i.e., AlSi10Mg) 5 mm-diameter support pillars with a fixed height of 5 mm containing varying filet angles and build orientations (i.e., 0 deg, 10 deg, 20 deg, 30 deg, 40 deg, 50 deg, and 60 deg from the normal surface) to determine surface roughness and water wettability effects. From experiments, anisotropic wetting was observed due in part to the surface heterogeneity created by the LPBF process. The powder-sourced AlSi10Mg alloy, typically hydrophobic, exhibited primarily hydrophilic behavior for build angles of 0 deg and 60 deg, a mix of hydrophobic and hydrophilic behavior at build angles of 10 deg and 20 deg, and hydrophobic behavior at 30 deg, 40 deg, and 50 deg build angles. Measured surface roughness, Ra, ranged from 5 to 36 µm and varied based on location. 3D-topography maps were generated, and arithmetic mean heights, Sa, of 15.52–21.71 µm were observed; the anisotropy of roughness altered the wetting behavior, thereby prompting some hydrophilic behavior. Build angles of 30 deg and 40 deg provided for the smoothest surfaces. A significantly rougher surface was found for the 50 deg build angle. This abnormally high roughness is attributed to the melt pool contact angle having maximal capillarity with the surrounding powder bed. In this study, the critical melt pool contact angle was near equal to the build angle, suggesting that a critical build angle exists, which gives rise to pronounced melt pool wetting behavior and increased surface roughness due to enhanced wicking followed by solidification.
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- Award ID(s):
- 1828571
- NSF-PAR ID:
- 10341174
- Date Published:
- Journal Name:
- Journal of Manufacturing Science and Engineering
- Volume:
- 144
- Issue:
- 8
- ISSN:
- 1087-1357
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4053608
