高温高强亚稳态AlRETM铝合金氧化与腐蚀机理的研究

Through an overview on the world’s development of non-equilibria-phased aluminum alloys, the most recently emerging “high temperature high-strength aluminum alloys” has been pinpointed due to the merit in the integrated properties of “high strength-to-weight ratio, pronounced strength at high temperatures and outstanding corrosion resistance” over their traditional counterparts such as Al, Mg, Cu, Fe, Co and Ni-based alloys. As such, in light of their tremendous value in science and technology and world-wide crucially core and fundamental issues that need to be explored, the non-equilibria-phased AlRETM alloys that have exhibited outstanding strength at room and high temperatures and super corrosion resistance in our previous experiments are proposed in this proposal for further scrutizing and penetrating investigation on the unique strengthening mechanism, high temperature oxidation and hot corrosion behavior of the very non-equilibria phases. In particular, the oxidation behavior under static and cyclic conditions and the properties of the quasi-stable alloys associated with oxidation films in resistance to mechanical and corrosion effects are highlighted. Besides, optimization on the stability of the “non-equilibria-phased alloy and oxidation film” will be conducted to maintain these super properties in service for long time. From this project, an advanced and forefront scientific area of “the high temperature high-strength non-equilibria-phased AlRETM alloys” will be established, which will also be contributed to advanced technological development and application in aeronautical, space and national defense industries.

本项目全面剖析了国内外非平衡态铝合金发展历史、现状与态势，敏锐抓住崭新“高温高强铝合金”超越“传统铝合金无法高温服役”和“其它合金Mg、Cu、Fe、Co、Ni”不可比拟的“高强重比、高热强与高抗蚀”三位一体的“新兴合金”，瞄准国际共性核心关键前沿基础问题及其巨大科技发展价值，以我们已经获得显著力学、热强和抗蚀的非平衡态AlRETM合金为对象，就其“最佳强度、热强和抗蚀”的非平衡态合金组织的“强化机制、高温氧化和热腐蚀特征属性”及“合金/氧化膜”整体性能优化继续拓展国际前沿开辟国内外首创科学研究，着重从亚稳态铝合金在300-650 C静态和动态氧化规律、机制、抵抗力学和腐蚀属性研究入手，从非平衡态“材料组织学、机械性能、氧化、热腐蚀、电化学、热力学、优化稳定”多学科建起一个完备的“高温高强非平衡态AlRETM铝合金”新兴前沿科学理论体系，为航空航天国防重大领域提供新兴技术支撑。

AlReTm合金因高强、高抗蚀、高温服役成为国际前沿热门材料。通过4年研究解决国际共性核心问题，完成目标取得重要成果，对推进空天、国防和民用工程重要应用具有非常价值，研究表明：.a. 非平衡态铝合金强韧热强性到底有多高、强化机理是什么？.AlReTm从完全非晶到完全晶态要经过纳米团簇形核（第一起始结晶温度Tx1）和长大（第二起始结晶温度Tx2）。在第一与第二结晶温度间长时退火致非晶AlReTm合金母体析出纳米晶，由固溶强化、沉淀硬化、晶粒细化、晶界强化与钉扎复合机理提高该合金强度到1600MPa、比强480MPacm3 g-1、热强达350 C。.b. 该合金钝化或氧化膜抗蚀性到底有多高、防护原理是什么？.自然钝化形成的氧化膜由于在完全非晶或非晶与纳米晶复合基体上形成，具有非晶结构，同时由于生长缓慢致钝化膜机械物理化学电化学均一致密而具有优异抗蚀和力学能力，保护机制就是该钝化膜集机械致密物理隔离电化学均一的综合俱佳本征属性。其优异属性可维系在低于Tx2下使用，抗蚀达10E-8A/cm2。.不同于钝化膜，在高于Tx2下氧化，合金从完全非晶向全晶转变，导致氧化膜不再保持非晶而变成复合晶体氧化膜，二是氧化膜生长速率远比钝化膜快使致密下降、缺陷多、力学性能下降、电化学属性不均，其抗蚀性类似于传统铝合金10E-6A/cm2，并随合金成分氧化温度时间降到10E-5A/cm2。.c. 什么成分织构措施能稳定保持其常/高温下最大强韧和抗蚀性？.AlReTm在Tx1与Tx2间退火需漫长纳米晶形核长大，若在Tp2左右退火仅需较短时间完成纳米晶形核长大，在非晶母体镶嵌均匀分布晶粒5±2nm晶簇复合织构，具有最佳机械化学电化学性能。纳米晶形核长大由合金成分、温度时间控制，遵从热力学动力学原理，符合Kissinger与Johnson-Mehl-Avrami规律，在低于Tx2下可保持最好机械抗蚀耐高温持久稳定性。