Synthesis of the FeTi intermetallic compound via amorphization and mechanochemical processing of elemental Fe and Ti powders

This study elucidates the mechanism of TiFe intermetallic formation via mechanochemical alloying, addressing contradictory literature data on phase transformation pathways. We investigated the structural evolution of elemental Fe and Ti powders milled at 1820 rpm for up to 300 s, followed by homogenizing heat treatment. Results indicate that mechanical activation drives the system into a highly disordered X-ray amorphous state, characterized by severe lattice strain rather than local particle melting. The unit cell parameter a of α-Fe remained unchanged (0.2867 ± 5 × 10 −4 nm), while the c/a ratio of α-Ti decreased from 1.5854 to 1.5479, confirming that TiFe nucleation occurs primarily within the distorted titanium lattice. Mechanochemical treatment reduced the coherently diffracting domain sizes to 26 nm (α-Fe) and 18 nm (α-Ti), causing a ∼9-fold and ∼4-fold increase in dislocation density for α-Ti and α-Fe, respectively. Subsequent annealing at 800 °C increased the TiFe phase fraction from 2% to 23%. However, complete single-phase synthesis was hindered by residual elemental peaks and the concurrent formation of the non-hydrogen-absorbing Fe 22 Ti phase (up to 36%). We conclude that Fe 2 Ti precipitation is driven by local chemical inhomogeneities exacerbated by high-temperature annealing. These findings clarify the role of the X-ray amorphous phase as a transitional nanocrystalline state and highlight the critical trade-off between TiFe crystallization and secondary phase suppression, offering guidelines for optimizing solid-state hydrogen storage materials.