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Melt infiltration of ceramic preforms for functionally graded materials

Erdamar, Caner
The aim of this work was to produce ceramic-metal composite which shows combination of high hardness and high flexural strength by a combination of hard front layer and tough back layer by Functionally Graded Materials (FGM) process. Composition is the most important variable to obtain gradual changing green/bulk density and/or porosity which are the requirements of an FGM sample. Three different layers of FGM with gradual changing green density and/or porosity were pressed following by ball milling of different weight % of boron carbide and silicon carbide particles with different particle sizes. Each green body was sintered, and then, pressure melt infiltration process was applied to fill porosities with aluminum alloy in order to reach the near theoretical density. Finally, the material was characterized by phase analysis, particle size and distribution analysis, green/bulk density and porosity measurements, optical microscope and SEM analyses, three point bending test, hardness measurement and XRD analysis. Flexural strength measured for FGM B4CSiC-Al composites having dimensions of 12 cm length, 4 cm width, 2.3 cm thickness is nearly 348 ± 40 MPa.