Deformability, inherent mechanical properties and chemical bonding of Al11Nd3 in Al-Nd target material

Abstract

Microstructure uniformity of the Al-Nd target materials with Al11Nd3 significantly affects the performance of the fabricated Al-Nd film, which is widely used as wiring material in large-size thin-film transistor liquid crystal display (TFT-LCD) panels. Understanding the inherent mechanical properties and chemical bonds of Al11Nd3 is crucial for homogenizing the Al-Nd target. Here, by a combined experimental and ab-initio theoretical study, the microstructure and deformability of the Al-3wt%Nd alloy and the inherent mechanical properties and chemical bonds of Al11Nd3 were investigated comprehensively. The Al-3 wt%Nd alloy is composed of the pre-eutectic α-Al matrix and the eutectic α-Al and a high stable α-Al11Nd3 phase. During the plastic deformation, the eutectic microstructure transforms from a cellular to a lamellar shape, while the morphology and dimension of α-Al11Nd3 are not changed significantly. By examining ideal tensile strength, elastic moduli, hardness and brittleness-ductility, the hardness-brittleness of α-Al11Nd3 is quantitatively evaluated, accounting for its difficulties of plastic deformation and fragmentation. Combining band structure, population analysis, topological analysis and crystal orbital Hamilton population, we found that α-Al11Nd3 possesses two types of chemical bonds: the Nd-Al and Al-Al bonds. The former is a typical ionic bond with electron transfer from Nd to Al, while the latter, dominated by both 3s-3p and 3p-3p interactions, is a weak covalent bond. The mixed chemical bond is responsible for the high hardness-brittleness of α-Al11Nd3. This work is expected to lay a foundation for Al-Nd alloy and catalyze the fabrication of high-quality Al-Nd target materials.