الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
Abstract
Stir casting method was used to produce conventional metal matrix composites (MMC) with fairly homogenous dispersion of reinforcement material. Al-6061 and silicon carbide particles (15 μm) were selected as matrix and reinforcement materials respectively. The composites material were adjusted to contain 5% and 7.5% volume fraction of SiC. The matrix was first completely melt and kept for homogenizing at 750ºC. Then SiC powder preheated to 800 ᵒC was added during stirring action and when the vortex appeared. 1%wt of Mg was added to molten metal to improve wettability between the matrix and reinforcement. The melt mixture was poured into a metallic mold. The as-cast composites were processed by Equal Channel Angular Pressing (ECAP) route Bc at 300ᵒC. The microstructure and mechanical properties were studied for as-cast and ECAPed specimen.
Results showed that as-cast Al-SiC composites can be successfully fabricated using stir casting technique as the simplest and the cheapest method. The maximum porosity and agglomeration level for as-cast composites reached 2.75% and 0.35%, respectively, for 5%SiC while that for 7.5% SiC was 3.93% and 0.8%. Adding the SiC by 5% in the matrix increased the strength, while it decreased for 7.5%SiC. The hardness continued to increase by increasing the SiC content for all compositions.
After ECAP the porosity and the agglomerations level were decreased to 1.03% and 0.07% for 5%SiC and decreased to 2.02% and 0.16% for 7.5%SiC. The mechanical properties improved after the ECAP technique, for all compositions, up to the second pass and also the particles size was reduced from 15µm to reach 7.9µm after six passes for Al-5%SiC and to 7.5µm after four passes for Al-7.5%SiC. Maximum proof stress and maximum strength were 176 MPa and 228 MPa, after second pass for Al-5%SiC, respectively. In case of 7.5%SiC the proof stress and the strength reached 92 MPa and 153.3 MPa, respectively. Hardness have increased up to second pass for all compositions, where the maximum values were 88.3 and 94.3 HV for Al-5%SiC and Al-7.5%SiC respectively. The ductility increases with the ECAP passes, where it reached 13.9% and 13.5% in case of 5%SiC after 2nd pass and 7.5%SiC after 4th pass.