Al-pb Metal Film Interface Structure

Al-Pb binary alloy is one of the typical immiscible alloys. It draw a lot attention owing to the complementary both in chemistry and physics of Al and Pb, the superheating and supercooling phenomenon, the superconducting phenomenon, and so on. So it is very important to investigate the interface structure of Al-Pb alloy.Miedema theory is used to design the immiscible alloy in this article in order to predict the best miscible ingredient with the biggest entropy value. And through magnetron sputtering technique, high entropy Al-Pb homogeneous thin film is successfully prepared. Meanwhile, the thin film interface structure is studied with its modulated wavelength of 4nm, 8nm and 16nm, and interface structure is also learned by First Principle and Molecular Dynamics in atomic level.SEM results shows that Al and Pb are well dispersed in thin film without obvious segregation. When the samples are annealing at 250℃and 350℃, Pb particles are precipitated from the film surface, and the particles will aggregate and grow with the elongation of the annealing treatment time. This phenomenon is coursed by Spinodal decomposition. When the film is heated, Pb in the film will get enough phase transforming driving force and precipitate on the surface of the film. XRD results suggest that the changes of Al characteristic diffraction peak before or after annealing treatment from none to some also confirm that. Before heat treatment, binary Al-Pb homogenous thin film has glass or nano structure owing to its high entropy, and the lead recovery and recrystallization temperature is at room temperature, then it is hard for lead to maintain glass structure, so there are only lead peaks in XRD diagram before heat treatment. But after heated, the entropy value of the film will drop sharply in the result of Al-Pb two phase separations, and this caused the appearance of Al peaks. XRD results also tell that there is a specified wavelength between 4nm and 16nm which can get the smallest grain size with highest entropy. Molecular dynamics results also say the irregular degree will reach the highest when the paricle size of the film is at about 1nm to 2nm.TEM results suggest the film which is almost transparent is consisted of small Al-Pb mechanical mixture with no obvious mass contrast or diffraction contrast. After aging, the Pb atom will gradually precipitate from the film and the precipitates have some certain crystallographic orientation, and this is in accordance with the results of First Principle.