Wear and friction behavior of nanosized TiB2 and TiO2 particle-reinforced casting A356 aluminum nanocomposites: A comparative study focusing on particle capture in matrix

In the present study, regarding the theoretical and practical aspects of nanoparticle capture in liquid-state processing of aluminum composite, different volume fractions of TiB2 and TiO2 nanopowders were incorporated into aluminum alloy via stir casting method. Hardness and sliding wear test were carried out to evaluate the mechanical properties of composites. The effects of wear load and reinforcement content on wear rate and friction coefficient of composites were examined. Microstructural studied showed that particle distribution in A356-TiB2 composites was more favorable than that of the A356-TiO2 samples. Results showed that nanoparticles were partially captured by aluminum matrix. With an increase in reinforcement content the amount of porosity and rejected nanoparticles increased. Regarding the wettability features of particles, the amount of introduced TiB2 powders was higher than that of TiO2 particles. A356-TiB2 composites showed higher mechanical properties compared with those of A356-TiO2 samples. Significant improvements in hardness and wear resistance were obtained in A356-1.5vol.% TiB2 composite. It was observed that the friction coefficient of the composites was lower than that of the non-reinforced alloy. With an increase in normal wear load, wear rate of composites increased and friction coefficient of reinforced samples decreased. Study on surface morphology of the worn surfaces showed both of the mild and sever wear mechanisms. The depth and number of grooves in worn surface of composites decreased with introduction of nanoparticles into matrix. The presence of oxide layers was detected on worn surface. Iron trace was observed in wear debris of samples.