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High-Zn AlZn alloys exhibited a high damping capacity but a low strength, which restricted their applications in many structural components under vibration conditions. To overcome this problem, grain refinement and alloying (by adding Mg, Cu and Zr) were employed to enhance the strength of high-Zn AlZn alloys while retaining the high damping capacity. In this work, fine-grained high-Zn AlZnMgCuZr alloys extruded at different extrusion ratios were achieved by a combination of melt spinning and hot extrusion. The rapidly-solidified and extruded alloys were observed to contain numerous second-phase particles (Zn and η-phase) at grain boundaries, high-density nano-sized precipitates (GP-zones and η′-phase) present in equiaxed α-Al grains, along with high solute solubility and many ribbon interfaces. These special microstructural features provided the high-Zn alloys with excellent room/high-temperature damping capacity and high strength. With increasing extrusion ratio, the damping capacity decreased gradually due to the reduction in the density of second-phase particles, the increases in both solute solubility of α-Al matrix and density of coherent GP-zones, and the improvement of bonding strength of ribbon interfaces. The overall high strength of the high-Zn alloys was attributed to strong grain refinement strengthening, solution strengthening and precipitation strengthening. |
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