Investigation on addition of B4C particles coated by nano-TiB2 on microstructure and mechanical behavior of Al-B4C composites

In this research, a casting system was designed for manufacturing Al-B4C composites in 5, 10 and 15 vol.%B4C, while two types of particles (non coated and coated with nano-TiB2 by sol-gel method) were added at 800 and 1000 degrees C. The resulting composites were tested for their mechanical properties and microstructure to study the effect of coating and temperature parameters. Mechanical properties such as tensile strength and hardness were higher in the case of coated particles in 1000 degrees C, compared to the similar samples in 800 degrees C and also the composites with non coated particles. It is also observed that these properties improve with increasing the fraction of particles (up to 10 vol.%). X-ray diffraction studies also confirmed the effective role of coating in appearing of boron carbide peak in diffraction patterns. Additionally, the distribution of B4C particles in the matrix is found to be more uniform in samples with coated particles. The wetability of particles with molten alloy was also improved. In general, the results show that manufacturing these composites by vortex method in case of using non coated boron carbide powders is not successful, while coating with nano-TiB2 and increasing casting temperature can improve the wetability and consequently the incorporation of particles.