Thermodynamically Prediction of in-Situ Al3Ti, Al3Zr Aluminides Formation in Friction Stir Processing Based on Effective Gibbs Free Energy Change of Formation (〖"∆G" 〗^"e" ) Model

In this study, Al-surface composite reinforced by in-situ formed  and  aluminide particles was fabricated by using friction stir processing (FSP). A rolled AA 3003-H14 aluminum alloy sheet and equal proportion of Zirconium and Titanium metal powders as reinforcement were used to fabricate Al-surface composite. Six FSP passes were applied to improve the distribution of reinforcing particles. Microstructural examinations were performed using scanning electron microscopy (SEM) and phase analysis was done by an X-ray diffraction (XRD) technique. Microstructural investigation revealed that due to the solid state chemical reactions,  and  aluminides have formed at the interface between the metal powders and the aluminum alloy matrix. Formation of these aluminides with in the span time of less than 40 s, was attributed to the activated thermomechanical condition induced by FSP. The effective Gibbs free energy change of formation ( ) model was used to thermodynamically predict the aluminide phase formation at the interface between the matrix and the reinforcing metal particles. The results of prediction, matched well with the experimental observations.