Abstract
Ti-Al alloys have good prospects in the aerospace, automobile, and other fields because of their excellent mechanical properties. However, the lack of high temperature oxidation resistance limits their practical applications. Various ways have been used to study their oxidation behaviors. Besides numerous experimental studies focused on the oxidation resistance properties of Ti-Al alloys, theoretical research based on first principles calculations has been carried out on the oxidation mechanisms on the atomic and electronic scales. In recent years, these theoretical studies have provided strong support for understanding the oxidation mechanisms and designing anti-oxidation modification measures. This review will focus on the surface oxidation reactions, element diffusion behaviors and interface bonding properties. The influencing mechanisms of alloying elements on the oxidation properties will be discussed in detail.
Highlights
Research Progress of First PrinciplesTi-Al intermetallic alloys show promising applications in the aerospace, vehicle, and other fields
There are two main pathways to improve the high-temperature oxidation resistance properties of Ti-Al alloys: one is to change the composition through element doping in order to improve the overall performance of the alloys; the other is through surface modification by forming an anti-oxidation film to protect the material matrix from oxidation, such as laser cladding and micro-arc oxidation
There is a high content of Al element in Ti-Al alloys, a single Al2 O3 layer cannot be formed in the oxidation process, mainly because of the close equilibrium oxygen partial pressure of Al/A12 O3 and Ti/TiO2 and the similar formation energies of the A12 O3 and TiO2 oxides [7]
Summary
Ti-Al intermetallic alloys show promising applications in the aerospace, vehicle, and other fields. There are some obstacles that hinder the applications of Ti-Al alloys, among them their oxidation behavior is one of the most critical problems Titanium and aluminum both are passivated metals, they will spontaneously form dense oxide films in an air environment at room temperature. For the Ti-Al alloys, the affinity energy difference between oxygen and metal elements in oxides TiO2 and Al2 O3 is very small [3], which leads to bonding competition between Ti and Al with oxygen at high temperature. The mixed oxides are not always dense and uniform, and are often accompanied by large nodular-like or needle-like TiO2 oxides Such irregular oxide layers are mixed with a large number of vacancies, crystal boundaries, and other defects, which provides diffusion paths for oxygen atoms into the alloy matrix and accelerates the progress of Ti-Al alloy oxidation. Ti-Al alloys and the effects of alloying elements on their oxidation resistance properties will be emphasized
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