CoCrFeNiAl系高熵合金薄膜的高通量制备及其塑性变形机理研究

High-entropy alloy thin films (HEATFs) show many excellent physical and chemical properties, and compared with the bulk high-entropy alloys (HEAs), the cost of the HEATFs can be effectively reduced. They can be deposited on the micro-electro-mechanical devices and enhance their surface hardness, wear resistance and corrosion resistance, hence improve their service life. However, little work has been done on the optimization of the HEATFs' composition and the investigation of the interface with the substrate. Furthermore, the plastic deformation mechanism of the HEATFs under loading is still unclear, which greatly restricts the HEATFs' extensive industrial applications. In this proposal, the HEATFs with multiple concentration gradients will be synthesized by combinatorial sputtering technique. And a high-throughput strategy will be applied to characterize the HEATFs' mechanical properties through parallel nanoindentation tests. Using this approach, the optimum composition of the HEATFs with excellent mechanical properties will be identified from the complex composition systems rapidly and efficiently. Then the interface between the HEATFs and the substrates will be studied. After that focus ion beams will be used to prepare nanopillars and T-shape samples on the HEATFs' surface, and their micromechanical properties will be studied by in situ scanning electronic microscopy and in situ transmission electronic microscopy systematically. Based on the real time experimental results, a reliable model will be built to explain the plastic deformation mechanism of the HEATFs, which would provide theoretical basis and technical guidance for their industrial applications.

高熵合金薄膜材料具有许多优异的物理和化学性能，而且相对于块体高熵合金材料可以有效地降低工业使用成本。将其沉积在关键的微电子和微机械器件上，可以显著地增加器件的表面硬度、耐磨性和耐蚀性，提高其使用寿命。然而，目前对于具有优异性能的高熵合金薄膜成分的快速高效筛选及其与基体的界面结合研究较少，且对其在加载环境下的微观变形机理尚不清楚，使其在工业上的广泛应用受到一定限制。本项目意在通过多靶共溅射高通量制备技术获得具有成分梯度分布的高熵合金薄膜，通过多点分布式纳米压痕测试薄膜性能，快速高效地筛选出性能优异的高熵合金薄膜成分，并研究薄膜与基体的界面结合问题；之后通过聚焦离子束技术在高熵合金薄膜表面制备出微纳米尺度样品，并利用原位扫描和原位透射技术对薄膜样品在加载环境下的微观塑性变形行为进行实时和系统的研究，建立起相应的微观变形机理模型，为高熵合金薄膜在工业上的应用提供理论基础和技术指导。

近年来，高熵合金薄膜由于其优异的物理和化学性能得到了诸多学者的关注。本项目中，通过脉冲激光沉积技术在室温将CoCrFeNiAl0.3和WNbMoTaV高熵合金薄膜沉积到硅基底上，同时用磁控溅射法制备了WNbMoTaV高熵合金薄膜作为比较。之后，对薄膜的相结构，微观显微形貌，化学成分，力学性能，电学性能及耐腐蚀行为进行了系统的研究。X射线图谱和扫描电子显微镜观察表明，利用脉冲激光沉积法制备的两种合金成分的薄膜均为非晶态结构，且薄膜表面均存在纳米级颗粒，而利用磁控溅射法制备的WNbMoTaV高熵合金薄膜呈现出典型的晶体结构。CoCrFeNiAl0.3高熵合金薄膜具有较高的纳米硬度，弹性模量较低。随着沉积时间的增加，弹性模量和纳米硬度呈现出先升高后降低的趋势，当沉积时间为2 小时时，弹性模量和纳米硬度达到最高值；电阻率方面，WNbMoTaV高熵合金薄膜固溶体晶体结构是非晶结构薄膜的六倍左右。腐蚀行为实验表明，非晶体结构的CoCrFeNiAl0.3和WNbMoTaV高熵合金薄膜均具有比316L不锈钢更高的耐腐蚀性，但晶体结构的WNbMoTaV高熵合金薄膜腐蚀性能较差。本项目的研究结果为制备非晶态高熵合金薄膜提供了一种新方法，并为深入研究高熵合金薄膜的力学性能和腐蚀行为打下基础。