Abstract
Silicon carbide particles-reinforced Al4Cu composites containing 2.5, 5 and 7.5 wt.% of reinforcement were fabricated using powder metallurgy (PM) technique. The sintered Al4Cu-SiC composites were solution treated for 6 h at two different temperatures (495 and 530 °C) and then aged at 180 °C for various aging periods (4, 12 and 24 h). Effects of heat treatment on the microstructural changes and microhardness were investigated by scanning electron microscope, transmission electron microscope, x-ray diffraction and microhardness tests. The results indicate the ceramic particles-reinforced Al4Cu matrix requires different heat treatment parameters compared to the unreinforced alloy. The applied solution temperature did not allow for thorough dissolution of alloy phases in the matrix material produced by PM route. However, in Al4Cu-SiC composites the main strengthening phase (Al2Cu) was uniformly distributed in the matrix. The solid-solution temperature increase affects the reduction in time to reach peak hardness. The highest increment in microhardness by aging treatment was observed for composite with the addition of 5 wt.% of SiC solution treated at 530 °C for 12 h (110 HV0.05).
Highlights
The wide range of applications of light metal-matrix composites (MMCs) has attracted the attention because of their increased mechanical properties
It has to be noted that the obtained properties of composite materials are significantly influenced by the chemical composition and the methodology used to consolidate the materials, which enables formulating permanent matrix–reinforcement bonding, and more importantly by the microstructural evolution associated with applied heat treatment procedure (Ref 1)
The addition of silicon carbide particles resulted in a decrease in the relative density, which remains constant regardless of the weight fraction of reinforcing phase and ranges from 95.87 to 94.99% of the theoretical density. As it results from the above-presented values of Archimedes density powder metallurgy, processed composites are characterized by a high degree of compaction and the porosity not exceeding 6%
Summary
The wide range of applications of light metal-matrix composites (MMCs) has attracted the attention because of their increased mechanical properties. One of the methods for improving the mechanical properties of aluminum alloys is heat treatment, which has a strong influence on the microstructure of the composites (Ref 2). Scientific sources report that on the one hand the rapid hardening of composite materials and attaining peak hardness much earlier has been observed compared to the unreinforced alloy, which could indicate the aging characteristic accelerated with the reinforcement (Ref [4, 5]). There are a number of factors influencing the nature of change in kinetics and magnitude of hardening during aging the MMCs, such as chemical composition of the matrix material, size, shape and weight fraction of reinforcement and the method of processing the composite, not to mention the applied heat treatment parameters (Ref [8, 9])
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