Prediction of Ti/Al 2O 3 interface reaction products by diffusion simulation

Abstract

A new scheme for prediction of interface reaction products at metal/ceramics interface has been suggested based on thermodynamic calculation and diffusion simulation. Basically, a diffusion controlled reaction and a build-up of a local equilibrium were assumed at the interface. The thermodynamic state at the interface before the formation of reaction product was regarded as to correspond to a metastable equilibrium between the two initial phases. To determine the boundary compositions, a multicomponent diffusion simulation was performed. Under the metastable equilibrium state, the driving forces of formation of all the other phases could be calculated. By selecting the phase with the highest driving force of formation as the first-forming interface reaction product, the order of formation as well as the interface layer sequence could be predicted. The present scheme was applied to the prediction of interface reaction between pure titanium and alumina at 1100°C. It was expected that TiAl always forms first at the beginning of the interface reaction, but the stability of TiAl depends on the oxygen potential in the Ti matrix. The effect of the initial Ti layer thickness on the stability of TiAl was also clarified.