铸造合金铸态组织与变形合金组织相比，具有独特性，例如:枝晶尺寸的不均匀性。最近发现在变质合金和颗粒增强金属基复合材料中可获得“蔷薇花状的迷宫”枝晶组织，其强塑性明显优于细小、均匀的等轴枝晶组织，尤其塑性提高显著，其强化机制用“Hall-Petch”公式不能得到满意的解释；同时，“蔷薇花状”枝晶能够细化析出相，进一步提高强塑性。但至今关于“蔷薇花状的迷宫”枝晶提高强塑性的机制和细化析出相的机制报道甚少。因此，本项目拟在以下几个新的重要科学问题上取得突破：揭示铸造纳米颗粒增强金属基复合材料中“蔷薇花状的迷宫”枝晶组织的形成机制；“蔷薇花状”枝晶细化析出相机制；“蔷薇花状”枝晶的强塑性机制，探索其与“Hall-Petch”公式的内在联系与相关性；“蔷薇花状”枝晶、析出相、纳米颗粒对室、高温强塑性影响机制。上述研究目标的实现将为铸造合金凝固理论、强韧化理论取得新突破提供重要的实验依据与理论参考。

Compared with the deforming alloy, the casting microstructure of the casting alloy possesses some unique characters, such as the inhomogeneity of the dendrite size. Recently, “the rosebush-like dendrite” is found in the modified casting alloys and particle reinforced metal matrix composites, and the strength and ductility of these alloys are much superior than these of the alloys with a small and uniform dendrite size, especially the obviously higher ductility of these alloys. However, the strengthening mechanism can’t be explained satisfactorily by Hall-Petch relation. Simultaneously, “the rosebush-like dendrite” can refine precipitates, which can further improve the strength and ductility. But so far, the report that “the rosebush-like dendrite” improves the strength and ductility of alloy and simultaneously refines precipitates is very limit. Therefore, this project will intend to made breakthroughs in the new important scientific issues, as follow: reveal the formation mechanism of “the rosebush-like dendrite” in the casting nano-sized particle reinforced metal matrix composites; reveal the refinement mechanism of the precipitates in “the rosebush-like dendrite” alloy; reveal the enhanced mechanism of the strength and ductility in “the rosebush-like dendrite” alloy, and explore the internal relation and correlation with Hall-Petch relation; reveal the effect mechanism of “the rosebush-like dendrite”, precipitates and nano-sized particle on the strength and ductility of the alloy at the room or elevated temperatures. This investigation goal will provide the significant experiment data and theoretical reference for new breakthroughs in the theory of the solidification , strengthening and toughning in the casting alloy.