Evaluating the elastic properties of Al2O3–Al FGMs by longitudinal and transverse ultrasonic bulk waves velocity features.

The present study aimed to investigate the elastic properties of functionally graded materials using ultrasonic bulk wave velocity features. To this end, three Al 2 O 3 –Al FGM samples were fabricated by spark plasma sintering method at three different temperatures (1050 °C, 1400 °C, and 1450 °C). In addition, two homogenous aluminum and alumina samples were fabricated to evaluate the properties of the initial materials using the initial powders. Ultrasonic pulse-echo technique was applied on fabricated samples in order to measure the longitudinal and transverse wave velocities. The elastic properties of the graded samples were obtained by wave velocity features and Archimedes density. The alumina and aluminum elastic modulus were measured as 394 and 70 GPa, respectively. The results indicated that increasing the sintering temperature from 1050 °C to 1400 °C and 1450 °C leads to considerable improvement in the average elastic modulus. The average elastic modulus of the graded bundle sintered at 1450 °C (308 GPa) was about 8.5% higher than that of the one sintered at 1400 °C (284 GPa). The microstructure analogies of samples illustrated micro-voids and phases agglomeration in all samples. The highest wave attenuation was observed in the graded sample with the lowest sintering temperature, i.e., the largest number of micro-voids caused the highest energy absorption in the graded bundle sintered at 1050 °C. [ABSTRACT FROM AUTHOR]