No abstract

No abstract

A simple interaction‐potential model has been established to calculate the higher order elastic constants of intermetallic YbAl2 in the temperature range from 10‐300K. Temperature dependent second and third order elastic constants are used for the determination of the ultrasonic attenuation, velocity, Grüneisen numbers, Acoustic‐coupling constants, and thermal relaxation time at the different temperatures. Temperature dependency of the ultrasonic properties of YbAl2 is similar at low temperatures to that of pure metals and the low carrier heavy fermion systems ‐ LaSb, YbAs and YbP having simple NaCl‐type structures. Thermal energy density makes significant contribution to the total attenuation in the compound at the higher temperatures from 100‐300K. Effect of the magnetic field on the ultrasonic attenuation is also evaluated using the magneto resistance data. At 100K, the effect of the magnetic field becomes insignificant. The attenuation decreases with the field at 3K to 50K.

The ultrasonic properties like elastic constant, ultrasonic velocity in the hexagonal structured nanocrystalline RuCo alloys have been studied along unique axis at room temperature. The second and third order elastic constants (SOEC & TOEC) have been calculated for these alloys using Lennard-Jones potential. The orientation dependent ultrasonic velocity has been also evaluated to study the anisotropic behaviour of these alloys. The velocities V L and V S1 have minima and maxima, respectively at 45° with unique axis of the crystal, while V S2 increases with the angle from unique axis. The inconsistent behaviour of angle-dependent velocities is associated to the action of second order elastic constants. Debye average ultrasonic velocities of these alloys are increasing with the angle and has maximum at 55° with unique axis at room temperature. Hence, when a ultrasonic wave travels at 55° with unique axis of these alloys, then the average ultrasonic velocity is found to be maximum. Elastic constants and density are mainly the affecting factor for anomalous behaviour of ultrasonic velocity in these alloys. The mechanical and ultrasonic properties of Co 0.75 Ru 0.25 alloy will be better than the other compounds due to their high SOEC, ultrasonic velocity and low ultrasonic attenuation. Co 0.75 Ru 0.25 alloy is more suitable for industrial and other uses, as it has the highest elastic constants and lowest ultrasonic attenuation in comparison to other of these alloys. The results of this investigation are discussed in correlation with other known thermophysical properties.