纳米晶NbMoTaW难熔高熵合金薄膜力学性能及其热稳定性

Mechanical Properties and Thermal Stability of Nanocrystalline NbMoTaW Refractory High Entropy Alloy Thin Films

目的研究高熵合金薄膜的形貌、结构、力学性能和热稳定性,并探究其潜在的应用价值。方法选取不同厚度的纳米晶NbMoTaW难熔高熵合金薄膜作为研究对象,通过直流磁控溅射制备薄膜样品,采用扫描电子显微镜(SEM)、原子力显微镜(AFM)进行薄膜形貌观测,利用能谱分析仪(EDS)和X射线衍射(XRD),对薄膜成分和结构进行分析,采用高分辨透射电子显微镜(HR-TEM)观测内部结构,利用纳米压痕仪和真空退火炉进行力学性能和热稳定性的检测。结果 NbMoTaW高熵合金薄膜为单相BCC结构,表面形貌和晶粒尺寸随薄膜厚度的变化而变化,随着薄膜厚度的减小,其硬度先增加后减小,在膜厚为250 nm时出现最大值(16.0 GPa)。薄膜经过800℃、2 h的真空退火后,晶粒尺寸没有明显长大,同时硬度也没有明显下降,呈现出良好的热稳定性。结论成功制备出热稳定性优异的纳米晶NbMoTaW难熔高熵合金薄膜,并通过调控薄膜的厚度来改变晶粒尺寸,从而研究高熵合金薄膜结构与性能之间的联系。

The paper aims to research morphology, structure, mechanical property, thermal stability and potential applica- tion values of high entropy alloy thin films （HEAFs）. Nanocrystalline NbMoTaW refractory high entropy alloy thin films （HEAFs） with a series of film thicknesses were selected to be fabricated by direct current magnetron sputtering. The scanning electron microscope （SEM） and Atomic force microscope （AFM） were used to observe the surface morphologies. The energy dispersive spectrometer （EDS） and X-ray diffraction （XRD） experiment were carried out to identify the composition and phase structure separately. High-resolution transmission electron microscopy （HR-TEM） was performed to observe the internal fea- tures. Nanoindentation and vacuum annealing instrument were conducted to detect the mechanical properties and thermal stabil- ities respectively. HEAFs were single BCC structure. The surface morphologies and the grain sizes varied with film thicknesses. The hardness decreased firstly and then increased with the increase of the film thickness. The maximum hardness （16.0 GPa） occurred to the 250 nm-thick HEAF. After vacuum heat treatment at 800 ~C for 2 h, the grain size and the hardness of NbMo- TaW HEAFs remained almost unchanged, indicating excellent thermal stability. Nanocystalline NbMoTaW refractory HEAFs of good thermal stability are fabricated successfully. In addition, the grain sizes were adjusted by varying film thicknesses to study the relationship between structure and properties of HEAFs.