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Research Papers

Selective Laser Melting Additive Manufacturing of Novel Aluminum Based Composites With Multiple Reinforcing Phases

[+] Author and Article Information
Dongdong Gu

College of Materials Science and Technology,
Nanjing University of Aeronautics and Astronautics (NUAA),
Yudao Street 29,
Nanjing 210016, China
Institute of Additive Manufacturing (3D Printing),
Nanjing University of Aeronautics and Astronautics (NUAA),
Yudao Street 29,
Nanjing 210016, China
e-mail: dongdonggu@nuaa.edu.cn

Fei Chang, Donghua Dai

College of Materials Science and Technology,
Nanjing University of Aeronautics and Astronautics (NUAA),
Yudao Street 29,
Nanjing 210016, China
Institute of Additive Manufacturing (3D Printing),
Nanjing University of Aeronautics and Astronautics (NUAA),
Yudao Street 29,
Nanjing 210016, China

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received July 4, 2014; final manuscript received October 20, 2014; published online December 12, 2014. Assoc. Editor: Z. J. Pei.

J. Manuf. Sci. Eng 137(2), 021010 (Apr 01, 2015) (11 pages) Paper No: MANU-14-1355; doi: 10.1115/1.4028925 History: Received July 04, 2014; Revised October 20, 2014; Online December 12, 2014

The selective laser melting (SLM), due to its unique additive manufacturing (AM) processing manner and laser-induced nonequilibrium rapid melting/solidification mechanism, has a promising potential in developing new metallic materials with tailored performance. In this work, SLM of the SiC/AlSi10Mg composites was performed to prepare the Al-based composites with the multiple reinforcing phases. The influence of the SLM processing parameters on the constitutional phases, microstructural features, and mechanical performance (e.g., densification, microhardness, and wear property) of the SLM-processed Al-based composites was studied. The reinforcing phases in the SLM-processed Al-based composites included the unmelted micron-sized SiC particles, the in situ formed micron-sized Al4SiC4 strips, and the in situ produced submicron Al4SiC4 particles. As the input laser energy density increased, the extent of the in situ reaction between the SiC particles and the Al matrix increased, resulting in the larger degree of the formation of Al4SiC4 reinforcement. The densification rate of the SLM-processed Al-based composite parts increased as the applied laser energy density increased. The sufficiently high density (∼96% theoretical density (TD)) was achieved for the laser linear energy density larger than 1000 J/m. Due to the generation of the multiple reinforcing phases, the elevated mechanical properties were obtained for the SLM-processed Al-based composites, showing a high microhardness of 214 HV0.1, a considerably low coefficient of friction (COF) of 0.39, and a reduced wear rate of 1.56 × 10−5 mm3 N−1 m−1. At an excessive laser energy input, the grain size of the in situ formed Al4SiC4 reinforcing phase, both the strip- and particle-structured Al4SiC4, increased markedly. The significant grain coarsening and the formation of the interfacial microscopic shrinkage porosity lowered the mechanical properties of the SLM-processed Al-based composites. These findings in the present work are applicable and/or transferrable to other laser-based powder processing processes, e.g., laser cladding, laser metal deposition, or laser engineered net shaping.

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Figures

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Fig. 1

SEM images showing the typical morphologies of the starting AlSi10Mg powder (a) and SiC powder (b) and the mixed SiC/AlSi10Mg powder (c)

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Fig. 2

Schematic of the SLM apparatus (a); scan strategy for the SLM process with the alternate X–Y scanning direction (b); schematic of the SLM process and the related SLM parameters (c); schematic of the working mechanism of the tribometer used in the wear/tribological properties tests (d)

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Fig. 3

Typical XRD spectra of the SLM-processed Al-based composite parts at the different laser linear energy densities (η)

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Fig. 4

FE-SEM images showing the microstructural characteristics of the SLM-processed Al-based composite parts at the different laser linear energy densities (η): (a) η = 800 J/m; (b) η = 900 J/m; (c) η = 1000 J/m; (d) η = 1100 J/m

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Fig. 5

High-magnification FE-SEM images showing the morphologies and distribution states of the reinforcing particles in the SLM-processed Al-based composite parts at the various laser linear energy densities (η): (a) η = 800 J/m; (b) η = 900 J/m; (c) η = 1000 J/m; (d) η = 1100 J/m

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Fig. 6

EDX results showing the chemical compositions collected in the different structures in the SLM-processed composites: (a) large-sized particle-shaped reinforcement (point 1 in Fig. 4(a)); (b) strip-structured reinforcement (point 2 in Fig. 4(c)); (c) small-sized particle-structured reinforcement (point 3 in Fig. 5(c))

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Fig. 7

Influence of the laser linear energy density on the relative densities and cross-sectional microstructures of the SLM-processed Al-based composite parts

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Fig. 8

Variations of the microhardness of the SLM-processed Al-based composite parts at the various laser linear energy densities (η)

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Fig. 9

The COF (a) and the resultant wear rate (b) of the SLM-processed Al-based composite parts using the different laser linear energy densities (η)

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Fig. 10

FE-SEM images showing the morphologies of the worn surfaces of the SLM-processed Al-based composite parts at the different laser linear energy densities (η): (a) η = 800 J/m; (b) η = 900 J/m; (c) η = 1000 J/m; (d) η = 1100 J/m

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Fig. 11.

High-magnification FE-SEM images showing the typical morphologies of the reinforcement on the worn surfaces of the SLM-processed Al-based composite parts at the different laser linear energy densities (η): (a) η = 800 J/m; (b) η = 900 J/m; (c) η = 1000 J/m; (d) η = 1100 J/m

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