Formation of alpha phase via pseudospinodal decomposition in Ti-Nb-Fe based alloys

Herein, the fine-scaled α phase precipitation during step-quench heat treatments in Ti‐15Nb‐3.0Fe and Ti‐11Nb‐3.5Fe (wt%) alloys was evaluated. Thermodynamic analyses suggest that Ti‐11Nb‐3.5Fe alloy should present homogenous α phase formation via the pseudospinodal mechanism when solution-treated and step-quenched at 450 °C, which is confirmed in this work. STEM-EDX measurements confirm the non-equilibrium state of the α phase precipitates, whose Nb content is significantly higher than that of the α phase laths obtained after solution heat treatment followed by furnace cooling. Fe seems to play an important role in the precipitation mechanism, and is depleted from α phase laths in a short aging time.