超强静磁场（≥15T）下电磁激振诱导的力/溶质效应对轴瓦合金定向凝固组织影响研究

The bearing alloy has a solidification property which is extremely easy to segregate. Homogeneous, high-performance bearing alloy cannot be prepared by the currently used solidification methods. Exploring the way to solve the problem of material preparation homogenization by electromagnetic vibration is not only expected to propose a new technology for the preparation of bearing alloy, but also helpful to provide an important theoretical reference for the homogenization preparation of other easily segregated alloys and high alloy materials. Although the homogenization of solidification structure can be promoted by electromagnetic vibration, the effect of the induced force/solute effect on the CET has not been determined. In order to realize the ultra-fine and high homogenization of the solidification structure of the easy-segregation alloy and high-alloy material, the electromagnetic vibration of super-high static magnetic field (≥15T) composited directional solidification was proposed in this project. From the perspective of force/solute effect, the influence mechanism of CET under electromagnetic vibration will be investigated. The optimal electromagnetic vibration parameters for the homogenization of bearing alloy will be discussed. The prediction model of electromagnetic vibration parameters, solidification structure and service performance will be constructed. The research of this project is expected to break through the traditional understanding of the mechanism of CET induced by electromagnetic vibration, and provide important reference and new idea for the homogenization of continuous casting ingot under electromagnetic vibration.

轴瓦合金具有极易偏析的凝固特性，目前普遍采用的凝固方法都无法制备出均质、高性能的轴瓦合金。探索采用电磁激振方法解决该类合金凝固方法制备的均质化问题，不仅有望提出轴瓦合金制备的新技术，还可为其他易偏析合金、高合金材料的均质化制备提供重要的理论借鉴。电磁激振虽然能促进凝固组织的均质化，但其诱导的力、溶质等效应在凝固组织CET转变过程中起到的作用尚未有定论。为更好实现易偏析合金、高合金材料凝固组织的超细化和高均质化，本项目提出超强静磁场（≥15T）电磁激振复合定向凝固的方法，分别从力、溶质效应角度，考察电磁激振作用下凝固组织CET转变机制，探讨获得均质轴瓦合金的最佳电磁激振参数，构建电磁激振参数、凝固组织、服役性能的预测模型。本项目的研究有望突破对电磁激振诱导凝固组织发生CET转变机制的传统认识，为电磁激振作用下连铸锭的均质化研究提供了重要借鉴和全新思路。

轴瓦合金是高性能中型/重载用汽油机、柴油机中重要的关键基础材料，目前普遍采用的凝固方法尚无法制备出细晶、高均质的轴瓦合金。本项目以Al-Sn-Cu轴瓦合金作为研究对象，在其定向凝固过程中引入电磁场，研究了多模式电磁场在合金枝晶与枝晶间所诱导的力与溶质效应对Al-Sn-Cu合金凝固组织CET转变的影响规律。共发表科技论文16篇，申请发明专利4件，培养硕博士研究生9人。主要研究结果包括：.1. 自主研发了超强静磁场下多模式电磁场耦合定向凝固设备，在Al-Sn-Cu合金定向凝固过程实现了多模式电流与强静磁场的耦合，通过液态金属快速淬火技术，可研究不同电磁场参数对易偏析合金凝固组织CET的影响规律；.2. 通过相同磁感应强度下不同直流电流密度实验，量化了Al-Sn-Cu合金定向凝固过程中诱导α-Al枝晶折断所需电磁体积力，并建立相应的电磁场下诱导Al-Sn-Cu合金凝固组织CET的力学模型；.3. 通过相同磁感应强度下不同电流模式（直流与脉冲）实验，构建了α-Al枝晶不同电磁体积力模式，即枝晶尖端与枝晶根部受力持续反向与周期性反向两种模式，提出枝晶尖端与根部受力持续反向模式下更容易诱导Al-Sn-Cu合金定向凝固组织CET；.4. 通过相同电流密度不同磁感应强度实验，在枝晶尺寸上构建了两种不同量级的电磁流动，提出电磁流动所诱导的溶质富集能诱导Al-Sn-Cu合金定向凝固组织的CET；.5. 通过对柱状晶与等轴晶Al-Sn-Cu合金棒坯铸态性能的表征，提出晶粒组织的CET能同时提升材料的硬度、屈服强度、抗拉强度及均匀延伸率。这种组织的细化对材料轧态/热处理态的力学性能具有显著的遗传性。