纳米(I-Phase+α-Mg)准共晶的临界半固态形成条件及生长机制

准晶因其独特的原子排列结构而具有优异的机械和物理性能，将准晶作为增强相引入到镁合金中可使综合性能显著提高，具有广阔的应用前景，但作为一种新兴材料，仍有许多关键应用基础理论问题不清楚，如纳米准共晶的临界半固态形成条件和生长机制等问题还有待深入研究。本项目通过由铸态至挤压态再到半固态加工的工艺路线，制备纳米准共晶增强镁合金，定量分析合金成分与准晶相含量的关系；揭示合金成分及工艺参数对纳米共晶层片间距、晶粒尺寸的影响规律；分析准晶相的演变过程及尺寸效应，并微观表征不同形貌的纳米准共晶组织；研究准共晶中I-Phase与α-Mg的位向关系及准晶相与α-Mg基体的位向关系；基于JH模型和TMK模型并耦合动力学效应揭示准共晶生长机制；明确纳米准共晶的临界半固态形成条件（合金成分、冷却速率和应力）。本项目研究成果将对准晶应用基础理论的发展具有重要的意义，同时对准晶增强镁合金的开发与应用具有重要的实际意义。

Icosahedral quasicrystal phases possess attractive mechanical and physical properties such as high strength, low friction coefficient, low surface energy and high thermal conductivity due to their peculiar lattice structure. Therefore, quasicrystals reinforced Mg alloys possess attractive comprehensive performances, and will also have wide application in the future. However, as a new materials, the researches on many key application basic theory questions of quasicrystals are deficient, such as critical semi-solid formation conditions and growth mechanism of nano (I-Phase + α-Mg) quasi-eutectic, on those the further researching are necessary. In this fund, nano (I-Phase + α-Mg) quasi-eutectic reinforced Mg alloys will be fabricated by the technological lines from foundry to semi-solid process via extrusion process. The relations of the I-Phase contents with the compositions of Mg alloys will be quantitative analyzed. The influence laws of compositions and technological parameters on the interlamellar spacing and grain size of nano (I-Phase + α-Mg) quasi-eutectic will be revealed. The evolution processes and size effect of I-Phase during different process states will be analyzed. The orientation relationship between quasi-eutectic I-Phase and α-Mg, and between I-Phase and α-Mg matrix will be researched. The growth mechanism of (I-Phase + α-Mg) quasi-eutectic will be revealed based on JH (Jackson-Hunt) and TMK (Trivedi-Magnin-Kurz) models with dynamical coupling. The critical semi-solid formation condition (compositions, cooling rate and stress) of nano (I-Phase+α-Mg) quasi-eutectic will be obtained. The researches on development of quasicrystals application basic theories have great significance, in addition, on the development and application of quasicrystals reinforced Mg alloys have great practical significance.