Microstructures And Damping Capacities Of Aluminum-zinc Alloys

A set of apparatus for measuring damping capacities of alloys was developed by the author. As the demand of low weight and high strength for high damping alloys, the composition of Aluminum alloys was determined as Al-20%Zn-6%Si-0.4%Mg (i.e. AZSM) by the orthogonal experiments. Furthermore, effects of alloyed elements, the modifying agents and heat-treatment on microstructures, damping capacities and mechanical properties of the AZSM alloy were studied. Finally, the damping mechanism of the AZSM alloy was proposed. The main results are as follows:1. The apparatus is fit for measuring sonic frequency damping capacities of alloys. The characteristics of it are low cost, simple structure and high measuring precision.2. The damping capacity and the intensity of the AZSM alloy were 3.45 x 10"3 and 264.6 MPa respectively.3. The effects of strengthening elements Cu and Mn on microstructure and configuration of the alloy were little, but they improved obviously the mechanic intensities and depress the damping capacity of the AZSM alloy in some sort.4. Trace elements Ti(B), mix Rare Earth with rich Ce and Zr salt could markedly refine the primary a dendrite crystals. The damping capacities of the AZSM alloy with the optimal addition were improved by 68.4%, 86.6% and 102.9% respectively.5. The comprehensive capacities of the AZSM alloy were markedly promoted than that of the as-cast AZSM alloy which was aged at 200 癈, air-cooled and furnace-cooled after solid-solution, aged at 90 癈 and aged in nature after solid-solution. Among the mentioned heat-treatment methods, the comprehensive capacity after natural ageing is best, the damping capacity and the intensity of solid-solution heat treated AZSM alloy after natural ageing for 7 days were 7. 0 x 10"3 and 264.6MPa respectively.6. The damping mechanism at ambient temperature is related to viscous motion of dislocation and interactions between dislocation with various point defects, the viscous sliding between the phase with rich Zn and primary a dendrite crystals and the micro-plastic deformation of the soft phase in the eutectic.