Characterization of High-Cycle Bending Fatigue Behaviors for Piston Aluminum Matrix SiO2 Nano-composites in Comparison with Aluminum–Silicon Alloys

Abstract

In automotive industries, one failure mechanism in engine pistons is due to the fatigue phenomenon. Therefore, to enhance fatigue properties of piston aluminum alloys is a major concern for designers. One reinforcement method could be the addition of nano-particles in the aluminum matrix. In this article, high-cycle fatigue properties of the aluminum matrix nano-composite were characterized under bending loadings and then compared to those of the aluminum–silicon alloy. For this objective, fully reversed bending fatigue tests were performed on standard specimens, based on the ISO-1143:2010 standard. Before testing, nano-composite samples were stir-casted by the addition of 1 wt% SiO2 nano-particles, and aluminum specimens were gravity-casted in a cast-iron mold. The microstructure of materials and the distribution of nano-particles in the aluminum matrix were evaluated by the optical microscopy and the field emission scanning electron microscopy. Experimental data indicated that nano-particles had a significant effect on the high-cycle fatigue lifetime. The reason for this improvement in high-cycle fatigue properties could be finer grains, higher hardness, the proper distribution of nano-particles in the aluminum matrix and stronger bonding strength at the Al/Si interface. However, based on fracture surfaces, all samples had the brittle behavior due to cleavage and quasi-cleavage marks.