铝合金熔体中Mg2Si生长过程的掺杂/吸附效应及其形貌调控

The effective control of morphology and size of primary Mg2Si in Al alloy melt is the key to fabricate Mg2Si/Al composites with meeting service condition need. During the growth process of primary Mg2Si, selective adding microelement atoms dope in the Mg2Si crystal lattice or adsorb on the growth interface of Mg2Si, which can effectively regulate the morphology and size of Mg2Si. Therefore, in this project, the growth morphology of primary Mg2Si in Al melt is chosen as the research object, and experimental analysis and computer simulation are adopted. The growth process and mechanism of Mg2Si under the condition of doping or adsorption is to be studied to illuminate the doping distribution characterization and adsorption law of typical elements, and clarify their influence on the growth of Mg2Si. Moreover, the doping/adsorption growth pattern of primary Mg2Si is to be established in terms of basic crystal growth theories and detailed observation of two- or three-dimensional morphology of Mg2Si phase, which subsequently reveals the morphological evolution of Mg2Si. These results can provide theoretical guidance and technical support for choosing microalloying elements and fabricating high-performance Mg2Si/Al composites. Further, it is of reference value for morphological control of similar reinforced particles.

铝合金熔体中初生Mg2Si形貌和尺寸的有效控制，是最终制备出满足实际服役条件需要的Mg2Si/Al复合材料的关键。在初生Mg2Si生长过程中，通过选择性添加微量元素，使其原子掺杂或吸附在Mg2Si晶格中或生长界面，可实现对Mg2Si最终形貌和尺寸的有效调控。因此，本项目拟以铝合金熔体中初生Mg2Si的生长形貌为研究对象，综合采用试验和计算机模拟相结合的手段，通过分析掺杂/吸附条件下的Mg2Si受控生长过程和内在生长机制，阐明典型元素晶格掺杂分布特性、表面吸附规律，明确其与Mg2Si生长的内在联系及影响机制；系统观察并分析Mg2Si不同生长阶段的二维/三维形貌特征，建立掺杂/吸附条件下Mg2Si相受控生长模型，进而揭示不同形貌间的相互转化机制，为微合金化组元的选择和高性能Mg2Si/Al复合材料的制备提供理论指导和技术支持，也为同类增强颗粒形貌控制提供借鉴和参考。

在Al-Mg2Si合金材料制备过程中通过控制Mg2Si的形核生长过程，实现对其形貌、尺寸、分布等因素的有效控制，是最终制备出满足实际服役条件需要的高性能材料的关键。本项目采用试验和计算相结合的方法，通过在Al-Mg2Si合金熔体中引入Sr、P元素，显著改善了合金中初生Mg2Si的尺寸和形貌，初生Mg2Si相由粗大枝晶状转变为细小规则多面体形貌。Sr元素选择性吸附在Mg2Si{100}晶面，抑制该晶面的生长速度。P元素对初生Mg2Si的作用体现在两方面：一是作用在形核阶段，以AlP的形式充当初生Mg2Si的形核衬底，增加形核数量，AlP(331)/Mg2Si(110)、Al终止AlP(100)/Mg2Si(211)和P终止AlP(100)/Mg2Si(211)的异质形核界面结构均可以稳定形成；二是P原子选择性吸附在初生Mg2Si某些晶面，抑制其生长，从而影响其最终形貌。同时，利用失重试验，动电位极化曲线等电化学测试手段，分析发现Mg2Si形貌改变可显著提高合金耐蚀性（3.5%NaCl溶液），合金中由于初生Mg2Si被细化且分布均匀，使得腐蚀坑的扩展受阻，因此相比于原合金呈现出更好的抗腐蚀性能。项目执行期间，已发表SCI论文8篇，申请国家发明专利3项，培养研究生3名。