Investigation of the Site Occupation of Atoms in Pure and Doped TiAl/Ti{sub}3Al Intermetallic

摘要

Titanium-aluminium alloys with additions of a third component are interesting materials for high temperature applications. Especially their low weight makes them almost perfect for usage e.g. in aero engines. Responsible for the mechanical properties is the γ/α{sub}2 dual phase structure. The third component is thought to improve the mechanical properties and oxidation resistance. Especially niobium is used in almost all TiAl-alloys. Dual-phase TiAl/Ti{sub}3Al alloys consisting of a lamellar structure, comprising γ-phase plus a small amount of α{sub}2-phase, with addition of 1, 5 and 10at.%Nb or 2at.%Ag were prepared. The samples were investigated by means of the field ion microscopy (FIM), the tomographic atom probe (TAP) and supporting TEM, HRTEM analysis. The influence of doping elements on the variation of the field evaporation and microstructural parameters in the γ-phase as studied by FIM and TAP will be reported in this contribution. A new algorithmic approach based on TAP results was developed to evaluate the site occupancies in such ordered structures. In addition, computer modelling and simulation of the field evaporation behaviour of the different species including the next neighbour interaction in a FIM specimen are performed for the first time.