纳米颗粒对铝基复合材料非平衡凝固过程中ɑ-Al形核、生长、演化和强韧性的影响规律及机制

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.

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。

本项目研究了Al-Ti-C燃烧合成体系、参数（Me比例、C源种类等）对燃烧合成陶瓷颗粒尺寸、形状的影响规律及作用机制。研究了不同陶瓷颗粒尺寸、形貌、数量对铝合金组织构型、室温高温强塑性、抗高温蠕变行为和抗磨损性能的影响规律和作用机制。研究了纳米颗粒对“蔷薇花状迷宫”枝晶组织形成的影响规律以及“蔷薇花状迷宫”枝晶组织对铸造铝合金的强塑性影响机制。研究了微米、纳米单一尺寸以及微米+纳米双尺寸TiCp对Al-Cu复合材料组织、室温强韧性、高温强韧性及抗高温蠕变的影响规律与作用机制。揭示出采用Al-Ti-C体系燃烧合成不同形状、微米和纳米尺寸TiCx颗粒的演变规律和调控机制；提出了Al-Ti-B4C体系燃烧合成微纳米尺度双相碳化物、硼化物陶瓷颗粒的生长形貌演化规律及机制。揭示出燃烧合成原位内生纳米、微纳米颗粒增强铝基复合材料的微观组织、室温和高温变形行为及强化机制；揭示出金属熔体内纳米颗粒对铸造铝基复合材料 -Al形核、生长成“蔷薇花状迷宫”枝晶组织动力学的影响规律及机制。揭示出“蔷薇花状迷宫”枝晶组织的铸造合金的强塑性机制。揭示出微米、纳米单一尺寸以及微米+纳米双尺寸TiCp对Al-Cu基复合材料组织、室温强韧性、高温强韧性及抗高温蠕变的影响规律与作用机制。.全面完成了本项目计划任务书的研究内容和预期研究成果，达到了预期总体研究目标。本项目运行期间，发表被SCI收录学术论文26篇；参加国际学术会议4人次，参加国内学术会议9人次；授权发明专利2项；培养博士研究生和硕士研究生11名，其中，毕业博士研究生5名，毕业硕士研究生6名。并实现了产业化应用。