Bilgehan Ögel

Microstructural characterization and tensile properties of hot pressed Al–SiC composites prepared from pure Al and Cu powders

Abstract A conventional hot pressing method was used to produce Al–Cu–SiC particulate metal matrix composites. The matrix alloy was prepared from elemental powders of Al and 5 wt.% Cu. The composite comprises 13.3 or 27.2 vol.% SiC p with an average size of 10 μm. The powder mixtures were hot pressed uniaxially under nitrogen atmosphere. It is shown that Cu aids in the formation of a liquid phase. Practically pore free structures are obtained after pressing at 600°C. Elastic modulus, tensile strength and yield strength values were improved with incorporation of the reinforcement in composites prepared by fine Al powder. The ductility, on the other hand, decreased sharply with increasing amount of strengthening phase.

Non-destructive microstructural characterization of aluminium matrix composites by ultrasonic techniques

Abstract In this study, an attempt was made to correlate the propagation of ultrasonic waves to various microstructural features in Al–SiC composites. The investigated parameters include the volume fraction, size, and distribution of the SiC-reinforcing particulate. Composites were fabricated by hot pressing of Al, Cu, and SiC powders. It has been shown that the ultrasonic velocity in all composites increased with an increase in SiC content. At identical volume fraction, changing the size of SiC particles did not affect the velocity. However, a segregation of SiC particles along the grain boundaries caused a decrease in ultrasonic velocity, which was attributed to the higher amount of residual porosity in segregated structures.

Effect of Feed Rate on Tool Wear in Milling of Al-4%Cu/B4 C p Composite

The effect of feed rate on tool wear in milling of B4C p reinforced aluminum metal matrix composites (MMCs), produced by liquid phase sintering method, was investigated. Milling experiments on these composites were conducted with three different types of cementide carbide tools (uncoated, double coated (TiN + TiAlN) and triple coated (TiCN + Al2O3 + TiN)) for three different feed rates of 0.15 mm/z, 0.20 mm/z, and 0.25 mm/z. After milling experiments, an optical microscope was used to measure the magnitude of flank wear on the tools. Flank wear limit value, (V B ) = 0.3 mm was selected as a reference value for comparison of these tools. On the other hand, tool wear mechanisms were examined with the help of a scanning electron microscope (SEM). Experimental results indicated that higher feed rates led to lower tool wear for all type of tools and coated tools exhibited better performance than uncoated tool with respect to the flank wear.

On the drop-weight testing of alumina/aluminum laminated composites

Laminated composites with ceramic front layers and metallic or composite backing layers have gained attractiveness as lightweight armours, as they exhibit the same ballistic performance with lower areal densities as compared to steels. Drop-weight testing (DWT) has potential for evaluating the low velocity impact behaviour of materials. This testing gives significant ideas and information about failure mechanisms and behaviour of materials under low velocity impact. In this study, DWT of alumina/aluminum laminated composites was done in order to investigate the effects of lamination type, density with respect to area and mechanical property of backing material on the low velocity ballistic performance of these composites. The experimental results showed that the laminated composite with ceramic front layer and aged-aluminum alloy as backing layer was the most effective among different investigated specimens against low velocity impact loads.