HRTEM investigation of diffusion in metallic-glass multilayer films

Here we present a data set on our research of diffusion in metallic glass multilayers. In the present data set we combined raw data from nanoindentation, SEM and TEM experiments. Lack of plasticity is one of the main disadvantages of metallic glasses. One of the solutions to this problem can be composite materials. Diffusion bonding is promising for composite fabrication. In the present work the diffusion process in glassy multilayer films was investigated. A combination of advanced TEM methods and precision sputtering techniques allows visualization and study of diffusion in amorphous metallic layers with high resolution. Multilayered films were obtained by RF sputter deposition of Zr-Cu and Zr-Pd. The multilayers were annealed under a high vacuum (10‒5 Pa) for 1 and 5 hours at 400oC, i.e. well below the crystallization temperatures but very close to the glass-transition temperatures of both types of glassy layer. The structural evolution in the deposited films was investigated by high-resolution transmission electron microscopy. It was observed that despite the big differences in the atomic mass and size, Pd and Cu have similar diffusion coefficients. Surprisingly, 1 hour of annealing results in formation of metastable copper nanocrystals in the Zr-Cu layers which, however, disappear after 5 h of annealing. This effect may be connected with nanovoid formation under a complex stress state evolving upon annealing, and is related to the exceptionally slow relaxation of the glassy layers sealed with a Ta overlayer.

本数据集收录了我们针对金属玻璃多层膜扩散行为开展研究的相关数据，整合了纳米压痕（nanoindentation）、扫描电子显微镜（Scanning Electron Microscope，SEM）及透射电子显微镜（Transmission Electron Microscopy，TEM）实验获取的原始数据。塑性不足是金属玻璃的核心缺陷之一，复合材料是解决该问题的可行方案之一，而扩散连接在复合材料制备领域具有可观应用前景。本研究针对非晶多层膜中的扩散过程展开探究，先进TEM表征手段与精密溅射技术的结合，可实现高分辨率下非晶金属层内扩散行为的可视化与研究。本研究通过射频（Radio Frequency，RF）溅射沉积法制备了Zr-Cu与Zr-Pd两类多层膜，并将其置于10⁻⁵ Pa的高真空环境中，在400℃下分别退火1小时与5小时——该温度远低于两类非晶层的晶化温度，但十分接近其玻璃化转变温度。研究采用高分辨透射电子显微镜对沉积态薄膜的结构演化进行了表征，结果发现，尽管钯（Palladium，Pd）与铜（Copper，Cu）的原子质量和原子尺寸存在显著差异，二者的扩散系数却十分相近。令人意外的是，退火1小时会在Zr-Cu层中形成亚稳态铜纳米晶，但该晶相在退火5小时后会完全消失。该现象可能与退火过程中演化出的复杂应力场下的纳米孔洞形成有关，同时与被钽（Tantalum，Ta）覆盖层封装的非晶层异常缓慢的弛豫过程密切相关。