One of the important parameters in electrical discharge machining is the presence of micro cracks on the workpiece surface (recast layer). Therefore, the aim of this study was to investigate the possibility of increasing the mechanical properties of aluminum surface by alloying elements (copper and nickel) diffusion to the recast layer and thus removing surface micro cracks. For this purpose, pulse on time and pulse current in with and without ultrasonic vibration have been considered as input parameters and the presence of surface micro cracks has been investigated using microscopic images. Also, the yield stress of the surface layer was calculated using the surface micro hardness. Based on the obtain results, surface without micro cracks has been created on the aluminum surface due to the diffusion of copper and nickel into the workpiece surface which increased aluminum surface yield strength from 90MPa to 280MPa without ultrasonic vibrations and to 310MPa while applying ultrasonic vibrations. In other words, ultrasonic vibrations cause an average of 20% increase in surface layer yield strength. In addition, according to the wear test, in the case of using ultrasonic vibration, improving the mechanical properties of the surface has caused thinner grooves on the aluminum surface. پرونده مقاله

In this study electrical discharge process was used to increase surface wear resistance of pure aluminum. Pulse-on-time and pulse current were considered as input parameters of the electrical discharge process. Experimental results reveal that the electrical discharge process is a successful method for improving the surface wear resistance of aluminum, so that this method has greatly increased the surface wear resistance of aluminum parts. Results indicate that with increase input parameters (pulse-on-time and pulse current) weight loss of the aluminum specimens is reduced and the wear resistance increases. The XRD analysis demonstrated that Al3Ni2 and AlCu intermetallic compound and Al4C3 were formed on alloyed surface. The presence of these compounds and hard particles at the surface increases the wear resistance. Also, friction coefficient measurements show that, after electrical discharge process and improving surface wear resistance, the friction coefficient slightly increased due to the presence of hard particles on the alloyed surface. پرونده مقاله