Elsevier

Acta Materialia

Volume 58, Issue 13, August 2010, Pages 4398-4405
Acta Materialia

Fabrication of Al6061 composite with high SiC particle loading by semi-solid powder processing

https://doi.org/10.1016/j.actamat.2010.04.036Get rights and content

Abstract

Aluminum alloys reinforced with silicon carbide (SiC) particles have been studied extensively for their favorable properties in structural and thermal applications. However, there has been only limited research into investigating the loading limit of a reinforcement phase of a metal matrix composite. In this paper, semi-solid powder processing (SPP), a fabrication method that exploits the unique behavior of a solid–liquid mixture, was used to synthesize SiC particle-reinforced Al6061. A high volume loading (>45 vol.%) of SiC in Al6061 matrix was investigated by varying the SiC loading volume fraction, forming pressure, SiC particle size and Al6061 particle size. The compaction and synthesis mechanism of the composite by SPP was discussed based on reinforcement phase compaction behavior and processing parameters. Microstructure, hardness, fracture surface and X-ray diffraction results were also analyzed. Results showed that SPP can achieve over 50 vol.% loading of SiC in Al6061 matrix with near theoretical density.

Introduction

Semi-solid powder processing (SPP) combines the advantages of powder metallurgy and semi-solid forming [1], [2], [3], [4], [5], [6], [7]. In contrast to traditional bulk semi-solid forming, the process enables the mixing of various powders for improved properties and eliminates post-processing steps required for powder metallurgy routes. A summary of various processing routes of SPP investigated by other researchers is shown in Fig. 1 [8], [9], [10], [11], [12], [13], [14], [15], [16], [17]. In general, four basic steps are involved in SPP: powder preparation, powder precompaction, heating and semi-solid forming. SPP has been applied to produce net-shaped metal matrix composites (MMCs) with low reinforcement loading (<30%). Previous work has demonstrated the potential to produce composites with high efficiency, low cost and good compositional control with promising microstructures [18], [19], [20], [21].

Although it has been more than 20 years since the introduction of SPP, no in-depth research has been conducted concerning high reinforcement loading conditions above 45 vol.%. Metals reinforced with high reinforcement loading is very attractive due to the modified properties such as high modulus and strength, low coefficient of thermal expansion, and improved thermal conductivity [22], [23], [24]. Methods including infiltration [25], [26], [27], casting [28], [29], [30], and powder metallurgy [31] have been investigated to fabricate metal matrix composites reinforced with high ceramic loadings. Several limitations were discussed as to the fabrication of high ceramic loading MMCs, such as difficulty in compositional control in casting, sintering balance [32] and ceramic powder percolation [33], [34] in powder metallurgy, and closed and half closed pore problems in infiltration casting [35], [36], [37], [38], [39].

In this paper, a matrix phase of aluminum alloy 6061 (Al6061) reinforced by silicon carbide (SiC) particles was used to understand the synthesis of composites with reinforcement loadings above 45 vol.% by SPP. Theoretical SiC loading limit of the SPP has been proposed and discussed. In addition, effects of processing parameters, which include SiC loading, applied pressure and matrix-reinforcement particle size, on microstructure and hardness have been studied.

Section snippets

Experimental procedures

The Al6061 powders and SiC particles were prepared by blending in a powder mixer (SPEX 8000M) for 8 min. The chemical composition of Al6061 powders obtained from Valimet Inc. is shown in Table 1. The size and distribution of Al6061 and SiC particles (AEE Inc.) are summarized in Table 2. The experimental setup for heating and compression is shown in Fig. 2. The die and powders were heated in the furnace (Applied Test System Inc.), while the load and movement of upper ram were controlled and

Results and discussion

The compaction curves of SPP are analyzed to understand the synthesis mechanism of Al6061–SiC composite and the SiC loading limit. Then, effects of processing parameters on the composite microstructure, hardness and fracture surface are discussed. In addition, the presence of aluminum carbide (Al4C3) is checked with X-ray diffraction analysis.

Conclusion

In this paper, SPP was used to fabricate Al6061 composite reinforced with high volume loading of SiC particles. The compaction and synthesis mechanism of Al6061–SiC composite was discussed, and the SiC loading limit was analyzed. The effects of the reinforcement particle size, matrix particle size, reinforcement loading volume and pressure on the microstructure and mechanical properties were investigated.

SPP of Al6061 composite for high loading SiC conditions had the following characteristics.

Acknowledgements

The authors greatly appreciate the financial support from the Ames Laboratory of US Department of Energy. Ames Laboratory is operated for the US DOE by Iowa State University under contract No. DE-AC02-07CH11358.

References (46)

  • G.-Y. Kim et al.

    J Manuf Sci Eng Trans ASME

    (2007)
  • C.M. Chen et al.

    J Mater Process Technol

    (2005)
  • L. Zu et al.

    J Mater Process Technol

    (2001)
  • R.W. Hamilton et al.

    Compos Part A: Appl Sci Manuf

    (2003)
  • S.-J. Luo et al.

    Trans Nonferr Met Soc China

    (2006)
  • C.M. Chen et al.

    Mater Sci Eng A

    (2005)
  • M.L.T. Guo et al.

    Compos Sci Technol

    (2000)
  • T. Fan

    Mater Sci Eng B

    (1998)
  • A. Miserez et al.

    Mater Sci Eng A – Struct Mater Proper Microstruct Process

    (2004)
  • L. Zhang et al.

    Mater Sci Eng A – Struct Mater Proper Microstruct Process

    (2008)
  • W.L. Prater

    Mater Sci Eng A – Struct Mater Proper Microstruct Process

    (2006)
  • M. Kouzeli et al.

    Acta Mater

    (2001)
  • O. Beffort et al.

    Compos Sci Technol

    (2007)
  • A. Kawasaki

    Ceram Int

    (1997)
  • F. Watari

    Compos Part B Eng

    (1997)
  • S.F. Corbin

    Mater Sci Eng A Struct Mater

    (1999)
  • K.-M. Cho et al.

    Mater Sci Forum

    (2004)
  • S.-C. Jeng et al.

    Acta Mater

    (1997)
  • W.Y. Kim et al.

    Mater Sci Eng A

    (2007)
  • N. Ramakrishnan

    Acta Mater

    (1996)
  • S. Qin et al.

    Mater Sci Eng A

    (1999)
  • L.M. Tham et al.

    Acta Mater

    (2001)
  • J.C. Lee

    Acta Mater

    (1997)
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