Microstructural Analysis of Thermo-Mechanical Processed Ti-6Al-4Fe Alloy

Microstructural analysis of a (alpha + beta) Ti alloy was investigated to consider phase transformation in each step of the thermo-mechanical process using by SEM and TEM EDS. The TAF (Ti-6Al-4Fe) alloy was thermo-mechanically treated with solid solution at 880 degrees C, rolling at 880 degrees C and annealing at 800 degrees C. In the STQ state, the TAF microstructure was composed of a normal hcp alpha and metastable beta phase. In a rolled state, it was composed of fine B2 precipitates in an alpha phase, which had high Fe segregation and a coherent relationship with the beta matrix. Finally, in the annealing state, the fine B2 precipitates had disappeared in the alpha phase and had gone to the boundary of the alpha and beta phase. On the other hand, in a lower rolling temperature of 704 degrees C, the B2 precipitates were more coarse in both the alpha and the boundary of alpha and beta phase. We concluded that microstructural change affects the mechanical properties of formability including rolling defects and cracks.