Abstract
SiCp reinforced aluminium matrix composites (AMCs), which are widely used in the aerospace, automotive, and electronic packaging fields along with others, are usually prepared by ex situ techniques. However, interfacial contamination and poor wettability of the ex situ techniques make further improvement in their comprehensive performance difficult. In this paper, SiCp reinforced AMCs with theoretical volume fractions of 15%, 20%, and 30% are prepared by powder metallurgy and in situ reaction via an Al-Si-C system. Moreover, a combined method of external addition and an in situ method is used to investigate the synergistic effect of ex situ and in situ SiCp on AMCs. SiC particles can be formed by an indirect reaction: 4Al + 3C → Al4C3 and Al4C3 + 3Si → 3SiC + 4Al. This reaction is mainly through the diffusion of Si, in which Si diffuses around Al4C3 and then reacts with Al4C3 to form SiCp. The in situ SiC particles have a smooth boundary, and the particle size is approximately 1–3 μm. A core-shell structure having good bonding with an aluminium matrix was generated, which consists of an ex situ SiC core and an in situ SiC shell with a thickness of 1–5 μm. The yield strength and ultimate tensile strength of in situ SiCp reinforced AMCs can be significantly increased with a constant ductility by adding 5% ex situ SiCp for Al-28Si-7C. The graphite particle size has a significant effect on the properties of the alloy. A criterion to determine whether Al4C3 is a complete reaction is achieved, and the forming mechanism of the core-shell structure is analysed.
Highlights
The yield strength and ultimate tensile strength of in situ SiC particles (SiCp) reinforced Aluminium matrix composites (AMCs) can be significantly increased with a constant ductility by adding 5% ex situ SiCp for Al-28Si-7C
Aluminium matrix composites (AMCs) are attractive materials for lightweight applications owing to their high strength-to-density ratio, good wear and fatigue resistance, and high-temperature mechanical properties
SiCp/AMCs were prepared with different volume fractions of SiCp by combining in
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Almost all existing methods for preparing SiCp-reinforced AMCs use ex situ techniques, such as rheocasting [4], infiltration [5], melt-stirring [6], and powder metallurgy techniques [7,8]. F. et al performed some research on in situ SiCp formation in an Al matrix [20,21] They designed a liquid-solid reaction to realise the in situ synthesis of SiCp in an Al melt and prepared SiCp-reinforced Al-18Si alloys by applying the casting method. Mokhnache et al synthesised Al2 O3 and SiC in situ from an Al-SiO2 -C system by reaction hot pressing, and the change in the Al4 C3 phase and its effect on the properties were discussed [22]. The effects of ex situ SiCp and in situ SiC on the evolution of the microstructure and mechanical properties were studied
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