Hierarchical microstructure and two-stage corrosion behavior of a high-performance near-eutectic Zn-Li alloy

• 作者: Zhen Li Zhang-Zhi Shi Hai-Jun Zhang Hua-Fang Li Yun Feng Lu-Ning Wang
• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2021,（21）
• 页码范围: 50-65
• 页数: 16页
• 语种: 英文

摘要

In order to improve mechanical and corrosion properties of biodegradable pure Zn,a knowledge-based microstructure design is performed on Zn-Li alloy system composed of hard β-LiZn4 and soft Zn phases.Precipitation and multi-modal grain structure are designed to toughen β-LiZn4 while strengthen Zn,resulting in high strength and high ductility for both the phases.Needle-like secondary Zn precipi-tates form in β-LiZn4,while fine-scale networks of string-like β-LiZn4 precipitates form in Zn with a tri-modal grain structure.As a result,near-eutectic Zn-0.48Li alloy with an outstanding combination of high strength and high ductility has been fabricated through hot-warm rolling,a novel fabrication process to realize the microstructure design.The as-rolled alloy has yield strength (YS) of 246 MPa,the ultimate tensile strength (UTS) of 395 MPa and elongation to failure (EL) of 47 ％.Immersion test in simulated body fluid (SBF) for 30 days reveals that Li-rich products form preferentially at initial stage,followed by Zn-rich products with prolonged time.Aqueous insoluble Li2CO3 forms a protective passivation film on the alloy surface,which suppresses the average corrosion rate from 81.2 μm/year at day one down dramatically to 18.2 μm/year at day five.Afterwards,the average corrosion rate increases slightly with decrease of Li2CO3 content,which undulates around the clinical requirements on corrosion resistance(i.e.,20 μm/year) claimed for biodegradable metal stents.