Influences of reinforcement and displacement rate on microstructure, mechanical properties and fracture behaviors of cylinder-head aluminum alloy

<p>In the present work, the material microstructure, mechanical properties and fracture behaviors of cylinder-head aluminum alloys were experimentally investigated under different displacement rates and with and without the reinforcement. By the addition of nano-clay-particles and the heat treatment, it was tried to improve mechanical properties of the base material. For this objective, after the fabrication of as-cast and nano-composite samples, respectively by gravity and stir-casting; tensile testing was done on standard samples at the displacement rate of 0.1, 1 and 10 mm/min. Then, the sensitivity analysis was performed on experimental data to find quantitatively effects of two parameters of the reinforcement and the displacement rate. In addition, the optical microscopy and the field-emission scanning electron microscopy were utilized for the microstructure and the fracture surface, plus the energy dispersive X-ray analysis. Obtained results indicated that the microstructure of the aluminum alloy was finer due to the reinforcement. Besides, both the ultimate strength and the elongation enhanced. The regression analysis implied that the strength was sensitive only to the reinforcement. Although the elongation was sensitive to both the reinforcement and the displacement rate. Investigations of fracture surfaces showed brittle behaviors with cleavage and quasi-cleavage marks.</p>