核/壳状梯度结构Al-Fe复合材料的设计、制备及力学性能研究

本项目以高强高韧Al-Fe化合物的微观设计、制备及机理分析为目标，采用机械合金化和快速烧结工艺（放电等离子烧结和微波烧结），原位制备出一种新颖的核/壳状复合梯度结构Al-Fe块体复合材料。核区域为微米晶纯Al，可以改善材料的塑性；壳区域为超细晶化合物，可以保证材料的高强度；核/壳过渡区域的晶粒尺寸、化学成分和相组成呈现三维梯度分布。主要研究内容包括：1.研究纯铁粉和纯铝粉的配比和粒径比、球磨和烧结工艺参数对核/壳两区域的晶粒尺寸、物相和体积分数的影响；2.探索在制备过程中的元素互扩散机制、化合物形成机理、晶粒尺寸演化规律；3.研究核壳两区域的应力应变场分布和协调变形机理、裂纹萌生和断裂机制；4.建立复合材料的微观组织与力学性能的定量关系，揭示强韧化机理。通过本项目的实施，优化核/壳复合梯度结构参数以获得Al-Fe复合材料强度塑性的最佳结合，为深入理解梯度结构材料强韧化机理提供有益参考。

The objective of the present project is the microstructure design, preparation and mechanism analysis of Al-Fe intermetallic with high strength and good ductility. The combination of mechanical alloying with rapid sintering (spark plasma sintering or microwave sintering) will be applied to prepare bulk Al-Fe composite with a novel compound gradient structure with the core/shell shape. In this unique structure, the “core” areas of pure Al with coarse grains can improve the ductility of materials, and the “shell” areas of Al-Fe intermetallic with ultrafine grains can retain high strength. A three-dimensional gradient distribution of grain sizes, chemical composition and phases will be formed in the transitional regions between the core and shell areas. Research will focus on: 1. the effects of the mixing ratio and particle size ratio of pure Fe powder and pure Al powder, and the process parameters of ball milling and sintering on the grain size, phases and volume fraction of the core and shell areas; 2. the mechanism of mutual diffusion of elements, the formation mechanism of intermetallic and the evolution of grain size during preparation; 3. the exploration of internal stress and strain distribution field and deformation compatibility of the core and shell areas, the crack nucleation and fracture mechanism; 4. the establishment of quantitative relationships between the microstructure and the mechanical properties of the composite with core/shell structure and understanding the strengthening and toughening mechanisms. Through the implementation of the project, the optimal combination of strength and ductility of the Al-Fe composite can be achieved by adjusting the parameters of the core/shell gradient structure, and it is expected to provide some valuable references for strengthening and toughening mechanisms of gradient structure materials.