Al/SiC composites with high reinforcement content prepared by PIM/pressure infiltration
Technical Paper: PIM International, Vol.1 No. 4 December 2007, pages 53-55, 1504 words
State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China
The preparation and thermo-physical properties of Al/SiC composites with high reinforcement content (65vol%) were investigated. In order to obtain the feedstock with a high powder loading, SiC mixtures containing fine and coarse powders were investigated to obtain the optimal particle packing. The experimental results indicated that the bimodal mixture containing 65% coarse particles are able to prepare the feedstock with a high powder loading and good flowability.
The composites fabricated by PIM/pressure infiltration have high densities and homogeneous microstructures. Additionally there is no interface reaction observed between the reinforcement and matrix by XRD analysis. The Al/SiC composites prepared by PIM/pressure infiltration have high thermal conductivities and low thermal expansion coefficients.
During the past decades, demands for materials with high performances for electronic packaging and thermal management became urgent, as the extent of chip integration in the semiconductor industry has increased dramatically . Particularly, Al/SiC composites with high reinforcement content have received great interest as potential materials due to their excellent thermo-physical properties such as low coefficient of thermal expansion (CTE), high thermal conductivity (TC) and low density [2-4]. However, sufficient low thermal expansion coefficients can only be obtained when the volume fraction of the reinforcement is high enough (above 60%). For Al/SiC composites with high reinforcement content, infiltration of SiC preforms by liquid aluminium has been confirmed to be a reliable and cost effective processing method for the manufacture of Al/SiC composites [5-8].
For the SiC preform, conventional fabrication techniques such as cold press and slurry casting can only prepare preforms with simple geometry and low dimensional tolerance. As a competitive manufacturing technology, powder injection moulding (PIM) is able to produce complex-shaped parts with near net shape and high production volumes . In the process of pressure infiltration, the interconnected pores are filled by the liquid aluminium in a short time and at a low temperature, which helps to enhance the density of the composite and limit the generation of the harmful interfacial reactions. As a result, PIM/pressure infiltration can be regarded as a potential manufacturing technology for preparing Al/SiC composites.
Further sections of this article include:
- Experimental procedures
- Results and discussion
- Optimisation for particle packing by bimodal mixtures
- Rheological behaviour of the feedstock
- Microstructures of composites
- Thermo-physical properties of composites
Figures and Tables:
Fig. 1 SEM photograph of SiC powder: (above) powder 1#; (below) powder 3#
Fig. 2 Effect of the coarse particle content on the fractional packing density
Fig. 3 Viscosity of the feedstock at various shear rates
Fig. 4 Optical micrographs of SiC/Al composites: (top) composite A, (middle) composite B, (bottom) composite C
Fig. 5 XRD for the composite
Fig. 6 Coefficients of thermal expansion for the composites (CTE)
Table 1 Characteristics of the SiC powder
Table 2 Densities of composites