Abstract
In the present work, in-situ metal matrix composites were fabricated through squeeze casting. The copper particles were dispersed with different weight percentages (3%, 6%, 10%, and 15%) into Al-12% Si piston alloy. Also, heat treatments were performed at 380 °C and 450 °C for holding times of 6 and 18 h. The microstructures, X-ray diffractometer (XRD) pattern, hardness, and wear characteristics were evaluated. The results showed that these copper particles have reacted with the aluminum under all of the aforementioned processing conditions resulting in the formation of fine copper aluminide intermetallics. Most of the intermetallics were CuAl2, while AlCu appeared in a small ratio. Additionally, these intermetallics were homogenously distributed within the alloy matrix with up to 6% Cu addition. The amounts of those intermetallics increased after performing heat treatment. Most of these intermetallics were CuAl2 at 380 °C, while the Cu-rich intermetallics appeared at 450 °C. Increasing the holding time to 18 h, however, led to grain coarsening and resulted in the formation of some cracks. The hardness of the resulting composite materials was improved. The hardness value reached to about 170 HV after heat treating at 380 °C for 8 h. The wear resistance of the resulting composite materials was remarkably improved, especially at lower additions of Cu and at the lower heat treatment temperature.
Highlights
Aluminum-silicon alloys and their metal matrix composites are widely used in aerospace and automobile industries due to their low density, good mechanical properties, and corrosion resistance [1]
Small diffraction peaks of CuAl2 intermetallic phase were detected, which that the Cu particles had reacted with the Al matrix forming CuAl intermetallics, as suggested by the proved that the Cu particles had reacted with the Al matrix 2forming CuAl2 intermetallics, as analysis.by the EDS analysis
An increase in the number of fine copper aluminide intermetallic particles that were formed led to a strengthening of Figure 12At shows the average hardness measurements at different heat treatment for the material
Summary
Aluminum-silicon alloys and their metal matrix composites are widely used in aerospace and automobile industries due to their low density, good mechanical properties, and corrosion resistance [1]. New techniques are required to increase the strength of the Al piston alloys For this purpose, adding hard particles to the Al alloy (forming metal matrix composites (MMCs)) and decreasing grain size are considered optimum solutions. In-situ intermetallic compounds provide a new family of reinforcement phases (CuAl2 , TiAl3 , FeAl3 , etc.) which possesses high specific strength, high specific modulus, and excellent wear properties at both ambient and elevated temperatures These reinforcements are formed in the matrix by reaction of the added element(s) with each other or with the matrix, so the resulting dispersed particles can be expected to be thermally stable and have strong interfacial bonding with the matrix [10]. The present work aimed to obtain a new Al-alloy-based in-situ-composite material by squeeze casting that possessed excellent mechanical properties for piston application
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