High damping capacity of Al-40Zn alloys with fine grain and eutectoid structures via Yb alloying

Undesirable damping capacity and mechanical properties resulted from coarse alpha-Al dendrites and network eutectoid structures of high-Zn aluminum casting alloys are the main problem restricting their practical applications. Rare-earth microalloying offers an effective means to improve the microstructure of Al alloys. Hence, in this study, the microstructure, damping capacities, and mechanical properties of newly developed Al-40Zn-xYb (x = 0, 0.1, 0.3, 0.5 wt%) cast alloys were systematically evaluated by optical microscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The experimental results indicated that Yb3Zn11 and YbZn2 intermetallic compounds were successively formed by adding Yb in Al-40Zn alloys. The alpha-Al grain and the alpha + eta eutectoid structures of the Al-40Zn alloy were significantly refined with increasing Yb content. Among them, the 0.3Yb alloy exhibited the smallest grain size (approximately 157 mu m) and the minimum interlamellar spacing of the alpha + eta eutectoid structures (approximately 243 nm). Moreover, the same alloy presented partial curved alpha + eta eutectoid structures. The 0.3Yb alloy possessed optimal damping capacity and mechanical properties; in comparison with Al-40Zn, the damping values of 0.3Yb increased by 74.7% at 300 K and by 32% at the internal friction peak P (approximately 563 K), whereas the yield strength, tensile strength, and elongation increased by 25.4%, 14.9%, and 58.6%, respectively. The remarkable improvement in damping capacity and mechanical properties was mainly attributed to the high density of grain boundaries (GBs) and fine alpha + eta structures. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Rare-earth microalloying was used to improve the microstructure of high-Zn aluminum casting alloys. The addition of Yb successfully refined the alpha-Al grain and alpha + eta eutectoid structures in the Al-40Zn alloys. The 0.3Yb alloy exhibited optimal damping capacity and mechanical properties due to its fine microstructure.