Microscopic Mechanism of the Surface Interaction between Liquid and Solid Metals

采用声发射、电子显微镜、扫描隧道显微镜、x射线光电子能谱和电子探针显微分析等技术研究了Al、Al合金和非晶合金Al_<87>Ni_<10>Ce_3的液态金属脆化（LME）。在非晶合金上沉积Ga可使非晶合金的断裂应力降低50%以上，并对非晶合金的锯齿形应力-应变曲线起到一定的平滑作用。在不同温度下，观察了未加载和加载的Al和Al合金样品的声发射。结果表明，即使在没有拉伸应力的情况下，Ga原子也能穿透晶界，并在外加应力的作用下加速了Ga原子的渗透。事实证明，这种声发射技术对于预测这些材料中LME的发生非常有用。采用扫描隧道显微镜研究了镓沉积铝单晶的详细表面形貌。获得的图像强烈提示Al-Ga合金的形成。我们注意到在玻璃基板上蒸发的Al薄膜上有异常的Ga扩散。经测量，扩散速度一般为几厘米/小时；该值取决于薄膜厚度、衬底温度和退火温度。利用原子力显微镜、电子显微镜、XPS和EPMA等研究了这种异常扩散的机理。

Liquid metal embrittlement (LME) of Al, Al alloys and amorphous alloy Al_<87>Ni_<10>Ce_3 was studied using various techniques such as acoustic emission, electron microscopy, scanning tunneling microscopy, x-ray photoelectron spectroscopy and electron probe micro analysis.Ga deposition on the amorphous alloy was found to cause an over 50% reduction in the fracture stress of the alloy, besides, to play a role somewhat in smoothing its serrated stress-strain curve. Acoustic emission was observed for both non-loaded and locaded samples of Al and Al alloys annealed at various temperatures. Results indicate that Ga atoms can penetrate the interior through grain boundaries even in the absence of tensile stress, and that the penetration of Ga atoms is accelerated by applied stress. This AE technique has proved to be very usefull for predicting the occurrence of LME in these materials.Scanning tunneling microscopy was employed to investigate the detailed surface appearance of Al single crystals deposited by Ga. The obtained images strongly suggested the formation of Al-Ga alloy.We noticed anomalous Ga diffusion over evaporated Al films on glass substrates. The diffusion velocity was measured to be typically a few cm/h ; the value depended on film thickness, substrate temperature and annealing temperature. The mechanism of this anomalous diffusion was investigated using atomic force microscopy, electron microscopy, XPS and EPMA.