Key Takeaways & Executive Findings
- •• LPBF successfully fabricates CNTs/AlSi10Mg composites with up to 2.0 wt.% CNTs, achieving uniform dispersion below 2.0 wt.%. • Optimal hardness of 143.3 HV is achieved at 1.0 wt.% CNTs and a laser scan speed of 1,300 mm/s. • Adding 2.0 wt.% CNTs reduces the coefficient of friction by ~14% and wear rate by ~30% compared to unreinforced AlSi10Mg. • CNTs refine the microstructure and enhance strengthening via Orowan mechanism and Hall-Petch effect, improving tribological performance.
Abstract
In this study, carbon nanotubes (CNTs)/AlSi10Mg composite parts with CNTs contents ranging from 0.0 to 2.0wt.% were successfully fabricated via laser powder bed fusion (LPBF) with laser scan speeds ranging from 900 to 1,900 mm·s-1. Uniform dispersion of CNTs in the powders can be achieved when their content is below 2.0wt.%. In the LPBF samples, the morphology of the CNTs is found to be directly related to their content. Especially, the length of CNTs in samples prepared by LPBF increases as the CNT content increases. The length of CNTs is approximately 200-300 nm in the 1.0wt.% CNTs/AlSi10Mg composites and approximately 500-1,000 nm in the 2.0wt.% CNTs/AlSi10Mg composites. The hardness of the composites reaches its highest value of 143.3 HV when the CNTs content is 1.0wt.% and the laser scan speed is 1,300 mm·s-1. It is found that the self-lubricating properties of the CNTs improve the tribological properties of the composites. The coefficient of friction (CoF) and wear rate of the samples decrease with increasing CNT content. At a CNTs content of 2.0wt.%, the CoF and wear rate of the composite decrease by approximately 14% and 30%, respectively, compared to the unreinforced matrix. The presence of CNTs leads to a more complete and refined network microstructure within the samples. Both the CNTs and the aluminum carbide contribute to the Orowan mechanism and the Hall-Petch effect within the matrix.
1. Introduction
Aluminum alloys are widely favored for aerospace and automotive applications due to their high specific strength. Among the various types of aluminum alloys, cast aluminum alloys are commonly used in engine components, where tribological performance is critical. However, cast aluminum alloys with limited wear resistance may not withstand the loads required for more demanding application environments [1, 2].
Incorporating high-performance particles or fibers to aluminum alloys can significantly enhance the wear resistance of the matrix. Research indicates that uniformly dispersed reinforcements within the aluminum matrix can effectively reduce wear loss [3, 4]. Numerous efforts, often involving complex processes, have been made to achieve an optimal distribution of these reinforcements [5-7].
Laser powder bed fusion (LPBF) is one of the most prominent additive manufacturing (AM) technologies, utilizing a laser to selectively melt spread powder to fabricate complex structures based on computer-aided design (CAD) data files [8]. Due to its advantageous solidification process, reinforcement can be controlled by melt pool convection at the microscale to achieve significant strengthening, showing great potential in the preparation of metal matrix composites.
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Li-yi Jiang, Chao-yi Shen, Ting-ting Liu, Chang-dong Zhang, Xiang Su, Wei-wei Xu, Bo-xiang Wang, Zhi-xiang Qi, Wen-he Liao (2025). Effect of CNT content on microstructure and tribological properties of CNTs/AlSi10Mg composites by LPBF. China Foundry. https://doi.org/10.1007/s41230-025-4118-x
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Frequently Asked Questions
What is the optimal CNT content for maximizing hardness in CNTs/AlSi10Mg composites fabricated by LPBF?
The optimal CNT content is 1.0 wt.%, which yields a maximum hardness of 143.3 HV when combined with a laser scan speed of 1,300 mm/s.
How does CNT content affect the tribological properties of the composites?
Increasing CNT content reduces both the coefficient of friction and wear rate. At 2.0 wt.% CNTs, the CoF decreases by approximately 14% and the wear rate by about 30% compared to the unreinforced matrix.
What is the role of CNTs in the microstructure of LPBF-fabricated composites?
CNTs promote a more complete and refined network microstructure, and contribute to strengthening via the Orowan mechanism and Hall-Petch effect, along with aluminum carbide formation.
Can uniform dispersion of CNTs be achieved in the powder feedstock?
Yes, uniform dispersion is achievable when the CNT content is below 2.0 wt.%. Above this threshold, agglomeration may occur.
What is the significance of this research for industrial applications?
The findings demonstrate that LPBF with CNT reinforcement can significantly enhance the wear resistance and hardness of AlSi10Mg components, making them suitable for demanding aerospace and automotive applications where tribological performance is critical.
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