AZ91D镁合金废屑半固态再生触变成型及传输机制研究

AZ91D magnesium alloy is the most widely used cast magnesium alloy. At the process of machining magnesium alloy parts and using, many magnesium alloy chips are produced. Remelting of machined chips is a common recycling process. The semi-solid recycling is a method that produce parts through extrusion casting process from chips at semi-solid state. The chips were get from the machining process or the parts over service life.This sturdy, according to the momentum transmission，mass transmission and heat transmission, investigate the technics, basic principle and method of semi-solid recycling to improve the quality of regeneration parts. And research on the inner law of the relationship between the quality of chips and combination of interface. In the investigation, deeply analyses are carry out about microstructures behavior and thixotropy, and the model of relationship between chips size, shape of chips, the surface quality of chips, heating temperature, and holding time. Getting the mechanisms of how micro information of semi-solid forming affect on the final part, and making constitutive model of liquid flow and solid deformation, from the analyses of chips semi-solid forming parameters statistic. The research build the theoretical basis for the industrial production of semi-solid recycling magnesium alloy and the promotion the use of the process. From the point of view of the whole industry chain, this study have a great significance of promotion the development and utilization of magnesium alloys, energy saving and reduction of emission, and the realization of green circle.

AZ91D是镁合金中应用最广泛、最成熟、最典型的镁合金，在机械加工和使用后形成大量废料，通常的再生方法是重熔。半固态再生方法是将加工过程中产生的废屑或将报废件加工成屑，经半固态再生直接挤压铸造成零件的一种方法。本研究以动量传输、热量传输和质量传输为主线，研究废屑半固态再生循环过程中，品位提高的基本原理和方法，探索废屑品位对半固态成型屑间界面融合的影响规律；从微观机理与宏观特征相结合的角度对半固态再生材料的组织结构和触变行为进行深入分析，建立屑尺寸、屑形状、屑表面状态及加热温度、保温时间的函数关系，并分析废屑形成半固态时特征参数的统计规律，从而获得废屑半固态再生成型宏观与微观信息对成型零件时的影响机制以及液相流动行为和固相变形行为本构模型，为镁合金废屑半固态再生的工业化生产及该工艺方法的推广应用奠定理论基础。在整个产业链范畴，对促进镁合金的开发利用、节能减排，实现绿色循环具有重要意义。

半固态再生技术是回收合金废屑或边角料，通过热压将废料压制成一定尺寸的致密的坯料，然后将坯料进行半固态等温处理，最后触变挤压铸造成型零件的一种工艺。该方法有效的解决了传统镁合金重熔再生过程中的烧损和氧化、回收效率低、对环境产生污染等问题。.本项目研究了AZ91D镁合金废屑尺寸、变形特征和氧含量对CRP压坯变形组织和半固态组织特征及均匀性的影响，分析了屑界面的融合，总结出连续加热和半固态等温处理过程中的半固态组织演变规律，从物理上和数学上阐明了半固态组织的球化机理和粗化机理。.采用半固态挤压铸造工艺成功制备了AZ91D镁合金汽车差速器支架，解决了半固态加工过程中易出现固液分离等技术问题，获得了工艺参数对产品微观组织和性能的影响，阐明了动量传输、热量传输和质量传输之间的联系，形成一套完整的AZ91D镁合金废屑半固态再生成型零件过程的基础理论。.同时制备了AZ91-xLa/Nd合金、固相再生了AZ31镁合金废屑、固相合成了AZ91D-Nd合金和AZ31-C复合材料、挤压铸造成型了Al-10Si-2.5Cu-0.8Fe-Mg合金发动机支架，并获得了工艺参数对微观组织和力学性能的影响规律，分析了断裂类型及断裂位置，研究界面断裂规律，讨论了界面结合机制和性能强化机制。.与日本东京大学杉山澄雄副教授、长冈技术科学大学镰土重晴教授展开交流，合作研究“镁合金半固态挤压铸造和固相再生”的工艺及机理问题。本项目为镁合金废屑半固态再生挤压铸造成型汽车零件的工业化生产奠定理论及实践基础。.发表论文10篇，其中SCI收录6篇，EI收录2篇，中文核心收录2篇；授权中国发明专利4项、实用新型专利1项。培养硕士研究生5名，培养博士研究生4名。