The Influence of Cooling Rate on the Damping Characteristics of the ZnAl27Cu2 Alloy

Abstract

The paper presents the results of damping coefficient tests on the ZnAl27Cu2 alloy (ZL27). The tested alloy was cast into five types of molds made of different materials (a steel mold with an ambient temperature of 20°C, a steel mold with a temperature of 100°C, a humid green sand mold, a dried green sand mold and a mold made of foundry gypsum mass). The thermophysical properties of these materials are different, and that's affecting the rate of heat absorption from the cast. Different mold materials affect obtaining different cooling rates. The cooling rate significantly affects the microstructure of the tested alloy. The specimens of investigate alloy were subjected to ultrasound and microscopic tests to assess the alloy structure. The damping coefficient has been calculated on the basis of specimen measurements obtained with the use of the signal echo method. Research shows that high structural fragmentation adversely affects the damping properties of alloys is confirmed. On the other hand, very low cooling rate, resulting in the formation of large, overgrown dendrites, does not guarantee the highest vibration damping capacity for this particular alloy. It turns out in this case a humid green sand mold, (cooling rate of 5.1 K/s) guarantees the best damping properties for the ZL27 alloy.

Keywords

• zinc alloys
• damping coefficient
• high-damping metals
• cooling rate
• ultrasound testing