镁-锌-钙系低合金镁合金GP区微结构调控及耐蚀性提高机制

面向汽车、电子等领域对高性能耐蚀镁合金迫切需求，针对含Ca镁合金“亚微米/微米第二相导致微电偶腐蚀严重”瓶颈难题，提出低合金化成分设计策略与形成原子尺度GP区微结构取代第二相新思路。围绕新型Mg-Zn-Ca系低合金GP区微结构形成与调控机制、基于GP区微结构调控耐蚀性提高机制关键科学问题，研究主、微合金元素对铸轧凝固组织共晶相形成及其热-力耦合加工下演变、回溶行为和溶质原子再分布规律；研究微量稀土添加和预变形后溶质原子钉扎位错对GP区微结构与低合金腐蚀行为的影响规律。揭示GP区微结构形成与调控机制，阐明基于GP区微结构调控的低合金耐蚀性提高机制。特色与创新之处：①基于稀土微合金化与溶质原子钉扎位错，实现GP区微结构组成、数量和分布调控，突破GP区调控难题；②建立GP区微结构与低合金耐蚀性构效关系，实现基于GP区微结构调控的耐蚀性提高；为发展强韧性与耐蚀性同时提高的新型镁合金提供支撑。

The present project is geared towards the urgent demands for high performance corrosion resistant magnesium (Mg) alloys in the fields of automobile and electronics, etc. For the bottleneck problems of “serious galvanic corrosion in Ca-containing Mg alloys caused between the submicron/micron secondary phases and Mg matrix”, we proposed a composition design strategy of low alloying and a novel approach of replacing the secondary phases with atomic scale G.P. Zone. Regarding the key scientific problems, i.e. mechanisms for formation and regulation of G.P. Zone structures together with enhanced corrosion resistance based on the regulation of G.P. Zone, the effects of main- and micro-alloying elements on the formation of eutectic phase during cast-rolling solidification, as well as the evolution and dissolution behavior of eutectic phase and the re-distribution of solutes during thermo-mechanical processes will be systematically studied in novel low-alloyed Mg-Zn-Ca series alloys. Furthermore, the influences of rare earth (RE) micro-alloying and pre-train induced pinned dislocation movement by solute atoms on the G.P. Zone structures and the corrosion behaviors of micro-alloying Mg alloys will be deeply investigated. This project aims to reveal the mechanisms for the formation and regulation of G.P. Zone structures and corrosion resistance improvement of low-alloyed Mg alloys based on G.P. Zone regulation. The innovations lie in: (i) based on RE micro-alloying and the pinned dislocation movement by solute atoms, achieving the composition, number density, and distribution control of G.P. Zone structures, and overcoming the challenge of G.P. Zone regulation; (ii) by building a relationship between G.P. Zone structures and the corrosion resistance of micro-alloyed Mg alloys, realizing an improved corrosion resistance based on G.P. Zone regulation. This work could provide support for the development of novel Mg alloys with simultaneously enhanced toughness and corrosion resistance.