超高压(1-10GPa)镁合金微结构调控及其原位力学/腐蚀性能研究

As a special light-metallic material with Chinese characteristics, the progresses on applied-foundational researches of magnesium alloys are attracting much attention. Two deficiencies viz. low strength and poor corrosion resistance have been made distinct achievements after years of investigations, respectively. However, there are still some limits in improving the strength and corrosion resistance simultaneously, which severely weakens the large-scale applications of magnesium alloys. Thus it became a crucial issue in the current research fields of magnesium alloys. In the previous researches, the applicant has found that a series of unique microstructures, such as super-fine dendrites, super-fine twins and fine cluster precipitates, can be obtained by ultrahigh pressure treatment. These new microstructures are closely related to their mechanical and corrosion properties. In this proposal, the formation mechanisms of microstructures under ultrahigh pressure conditions and the relationship between microstructures and strength/corrosion properties will be systematically investigated based on the preliminary results in terms of theoretical calculations, macro- experimental testing and in-situ observation by environmental spherical aberration-corrected electron microscope. The relationship of kinetics-pressure-properties of different microstructures will be established. The effect law of ultrahigh pressure on the formation of different microstructures will be elucidated. And then the deformation process and corrosion routes will be clarified on the atomic-scale confirmation. Finally, it expects to achieve a new strategy and technique to develop new magnesium alloys which bestows high strength in combination with outstanding corrosion resistance.

作为一类中国特色的轻金属材料，镁合金的应用基础研究进展备受人们关注。镁合金强度低和耐蚀性差的两大缺点经过多年攻关，已分别取得了显著成效。然而在如何同时提高镁合金强度与耐蚀性方面的手段十分有限，严重削弱了镁合金的大规模应用，已成为了当前镁合金研究领域的一大紧迫课题。申请人在前期研究工作中发现，镁合金超高压处理后可得到一系列特殊的微结构（超细枝晶，超细孪晶和超细团簇析出相），这类结构与合金强度和耐蚀性密切相关。本项目拟在前期基础上，通过结合理论计算、宏观实验和环境球差电镜原位观察，针对超高压下不同微结构形成机理、微结构与强度/腐蚀性能之间的相关性展开系统研究，建立不同微结构形成动力学-压力-性能的关联，阐明高压对不同类微结构形成的影响规律，从原子尺度上解析微结构的变形、腐蚀过程, 以期找到一种开发高强度、高耐蚀性镁合金的新策略和新技术。

针对强度与耐蚀性方面的手段十分有限,严重削弱了镁合金的大规模应用课题。在国家自然科学基金的资助下，已经顺利完全了本项目提出的全部内容。重点开展了三个方面的工作：1)提出了镁合金亚稳结构强韧性思路，并在此基础上，设计制备了一系列的新的亚稳强韧化新结构：双层梯度压缩孪晶、纳米孪晶-层错结构、位错-孪晶-层错结构，这种新的结构可以显著提高合金的强度而不损失其塑性。2)制备了高压单相固溶镁铝合金。3)利用环境球差电镜揭示了镁的氧化、还原机理，从原子尺度上，首次为镁合金腐蚀涂层设计和改性提供了直接依据。关于新的结构的稳定性的研究获得了新的面上基金的连续资助，深入开展相关课题研究。通过结合理论计算、宏观实验和环境球差电镜原位观察,针对超高压下不同微结构形成机理、微结构与强度/腐蚀性能之间的相关性展开系统研究, 建立不同微结构形成动力学-压力-性能的关联,阐明高压对不同类微结构形成的影响规律, 从原子尺度上解析微结构的变形、腐蚀过程，为开发高强度、高耐蚀性镁合金的新策略和新技术。发表高水平论文17篇，申请专利3项，转化1项。