Velocity and attenuation of ultrasonic wave in Al–Al2O3 nanocomposite and their correlation to microstructural evolution during synthesizing procedure

Abstract

Non-destructive pulse-echo ultrasonic testing was conducted to measure ultrasonic parameters, i.e. longitudinal velocity (Vl), shear velocity (Vs) and attenuation coefficient (α) in Al–Al2O3 nanocomposites. Elastic constants were also determined using the relationship between Vl and Vs. The aim was to reveal the correlation between ultrasonic parameters and the microstructural features of Al–Al2O3 nanocomposites. The effect of addition of Al2O3 nanoparticles on the Vl and Vs velocities is mainly attributed to variation in the elastic modulus of Al–Al2O3 nanocomposites. Both Vl and Vs velocities and Young's modulus (E) were found to vary approximately in linear fashion with the increase of Al2O3 content. A considerable effect of milling process on Vl and Vs velocities was revealed, where they increase by increasing the milling time. The increment of Vl and Vs is owing to refinement of Al particles, homogenous dispersion of Al2O3 and particularly reducing porosity by proceeding milling time. In addition, increasing of Al2O3 content, better dispersion uniformity of Al2O3 and refinement of Al particles contribute to increase α values. Elastic constants were found to vary in the same manner as ultrasonic velocities. Interestingly, the improvement in E values by increasing Al2O3 content and milling time is attained, while the ductility did not change significantly.

Keywords

• Non-destructive evaluation (NDE)
• Aluminum matrix composite (AMCs)
• Microstructure
• Ultrasonic velocity
• Ultrasonic attenuation