同步辐射原位观测高强韧高熵合金凝固过程的电磁场调控

Except the four big effect of high entropy alloys itself, eutectic high entropy alloys has excellent properties such as good stability, resistance to creep, good casting showing great application potential. But the current research about eutectic high entropy alloys is limited to a few system, and for the preparation and performance characterization of hypoeutectic high entropy alloys with high strength and ductility it is involved less, and even less reports on the influence of electromagnetic field on the organization performance of high entropy alloys , therefore, for this project the atomic radius difference, mixing enthalpy, valence electron concentration and d-orbit energy level combined with experimental are used to induce optimum composition of high entropy alloys with high strength and ductility, and then the electromagnetic technology is introduced to improve the growth behavior of each phase. By means of in situ synchrotron radiation and diffraction technology, the interface heat transfer, mass transfer regularity and crystal growth kinetics behavior of high entropy alloys with high strength and ductility are disclosed, the influence mechanism of the electromagnetic stirring and electromagnetic oscillation coming from the traveling wave magnetic field and pulsed magnetic field on the solidification process of high entropy alloys with high strength and ductility are revealed, finally achieve the target of the active control of the melt movement characteristics and solidification characteristics, finish the organization's refining and homogenizing, improve its high mechanical properties from low to high temperature. All these results will be helpful theoretically to design high entropy alloy composition, improve the high entropy solidification theory and the deformation strengthening mechanism.

共晶高熵合金除了具备高熵合金本身的四大效应之外，还具备良好的相稳定性、抗蠕变性、可铸造性等优异性能，具有很大应用潜力。但目前关于共晶高熵合金的研究仅限于少数几个体系，而对于强韧性俱佳的亚共晶高熵合金涉及较少，更缺少电磁场对其组织性能的影响的报道，为此，本项目首先借助于原子半径差异、混合焓、价电子浓度、d轨道能级并结合实验归纳出具有高强韧高熵合金的最佳成分，然后再引进电磁场技术对其各相的状态以及生长方式进行改善。借助于同步辐射原位成像与衍射技术，探索强韧性高熵合金界面前沿的传热、传质规律和晶体生长动力学行为，揭示行波磁场和脉冲磁场引发电磁搅拌和电磁振荡对强韧性高熵合金凝固过程的影响机制，达到主动其熔体运动特性、凝固特性的目标，实现组织的细化和均质化，提高其高低温力学性能。研究结果对于指导高熵合金成分设计、完善高熵凝固理论和形变强化机制均有重要理论研究价值。

在国家自然科学基金面上项目(51771041)的资助下，本项目针对强韧性俱佳的高熵合金体系的研究不足，以力学性能、摩擦学性能和耐腐蚀性能优化为出发点，借助于原子半径差异、混合焓、价电子浓度、d轨道能级并结合实验成功开发出CoFeNi2V0.5Mox、AlxCoFeNi2V0.5、AlCrFeNi2W0.2Nbx及AlCrFeNiW0.2Tix高熵合金成分，并对其微观组织、力学性能、摩擦学性能和耐腐蚀性能进行了研究，探索了成分-组织-性能间的内在联系，深入揭示了相关的机理。1）考察了电磁场技术对其各相的状态以及生长方式的改善，达到了主动控制其熔体运动特性、凝固特性的目标，实现了组织的细化和均质化，提高了其高低温力学性能。2）借助于同步辐射原位成像与衍射技术，探索了上述高熵合金晶体生长动力学行为，研究结果对于指导高熵合金成分设计、完善高熵凝固理论和形变强化机制均有重要理论研究价值。3）采用真空感应熔炼技术制备了公斤级高熵合金样品，研究了Al含量和形变热处理方式对CoFeNi2V0.5Mox、AlxCoFeNi2V0.5合金组织及拉伸性能的影响规律，发现开发的CoFeNi2V0.5Mo0.2合金的强塑性优于大部分已报到的铸态高熵合金。4）采用激光熔覆技术在Q235和304不锈钢基体上成功制备了具有不同相结构且综合性能良好的高熵合金涂层。考察了AlCrFeNi2W0.2Nbx、AlCrFeNiW0.2Tix高熵合金涂层的磨损率随载荷和滑动速率和合金成分的变化规律，揭示了AlCrFeNi2W0.2Nbx、AlCrFeNiW0.2Tix涂层表面在海水介质中形成了具有保护作用的“摩擦膜”形成机理，研究结果对于拓展高熵合金在海工装备的应用具有重要指导意义。在该项目的资助下共发表了论文24篇，获授权专利14项，申请中专利10项。培养博士3名，硕士7名。