Influence of the Cooling Rate on Damping Characteristics of the ZnAl4Cu1 Alloy

The paper presents the results of damping coefficient tests in the ZnAl4Cu1 alloy (ZL5). The damping coefficient has been calculated on the basis of specimen measurements obtained with the use of the signal echo method. The method consists in passing the ultrasonic wave through the tested material. The ultrasonic wave from a transmitting and receiving head passes through a specimen, bounces off its bottom surface and comes back to the measuring head in the form of a signal echo. Difference in the signal strength between the first and the second echo in relation to the distance travelled by the ultrasound wave is a measure of the material’s damping characteristics. The specimens were cast into three molds made of different materials, i.e. green sand, plaster and metal. Thermophysical properties of these materials are different what affecting the rate of heat absorption from the cast. Three series of specimens have been obtained which cooled at different rates. The specimens were then subjected to ultrasound and microscopic tests to assess the alloy structure. The internal alloy structure affects its damping properties to a great extent.