Damping behavior of ZA27 alloys doped with silicon

The ZA27 alloy doped with silicon possesses excellent wear-resistant properties, but the damping capacity of the alloy (i.e. Q^-1) has not been studied in detail. In this paper, the damping behaviors and relative dynamic modulus of the as-cast ZA27 alloy and ZA27 alloys doped with 4wt%Si (hereinafter ZA27-4%Si alloy) were investigated using a multifunctional internal friction apparatus and thus the damping mechanisms of the two alloys were analyzed. It was found that damping capacities of the two alloys increase with the increasing of temperature and decreasing of frequency, while it is independent of vibration amplitude. The damping capacities of the ZA27 alloy and ZA27-4%Si alloy are relatively high; the values of Q^-1 in ambient temperature are 6.87×10^-3 and 5.83×10^-3 respectively at a strain frequency of 1.0 Hz. The relative dynamic modulus of the two alloys increases when the vibrating frequency increases, and the modulus decreases as temperatures increases in ZA27 alloy. For ZA27-4%Si alloy, the modulus is independent of temperature lower than 100°C ; Above 100°C, it decreases slightly with the increasing of temperature. It can be concluded that the slipping of phase interfaces or the viscous sliding of grain boundary, dislocation's oscillation, the infinitesimal plastic deformation that was caused by the difference of elastic module and heat expansion coefficient between phases of the alloy yielded the damping of the alloys. Based on the experiment results, it is proposed that ZA27-4%Si is an excellent alloy with the properties of high damping, high strength, good wear-resistance, and proper for the sliding bearing alloys.