Influence of Al-5Ti-1B master alloy on microstructure and damping capacity of ZA27 alloy

The modification mechanism and damping capacity of conventional as-cast ZA27 alloy modified by Al-5Ti-1B master alloy were investigated. The cantilever beam technique was used for the measurement of damping capacity. As the experimental results showed, the commercial Al-5Ti-1B master alloy is a powerful modifier, it can decrease the grain size of Al-rich primary α phase greatly and transform its dendritic structure to a fine petal-like one. Meanwhile, it can improve the damping capacity greatly, and the best modification effect and highest damping capacity can be obtained at 0.088% Ti content. It is believed that Ti(Al, Zn)₃, TiAl₃, TiB₂ are effective nucleators to ZA27 alloy, the damping mechanism of ZA27 alloy is associated with the viscous sliding or slipping of the grain boundaries and phase interfaces. The more the grain boundaries and interfaces, the higher the damping capacity of ZA27 alloy can be obtained.