Solute-induced precipitation nanosized Ti-rich phase greatly enhances the plasticity of Mo-Ti-Zr alloys

To optimize the mechanical strength and ductility of low-oxygen Titanium-Zirconium-Molybdenum (LO-TZM) alloys, systematic solution-quenching heat treatment was applied to specimens with various oxygen concentrations. Remarkable microstructural evolution was observed in the alloy with an oxygen content of 280 ppm: nanoscale Ti-rich precipitates (∼20 nm in diameter) formed within the molybdenum (Mo) matrix. The refined microstructure yields an ultimate tensile strength of 733 MPa and exceptional ductility (28.7 % elongation). The stress–strain curve exhibited a distinct yield plateau accompanied by macroscopic Lüders band formation, evidencing substitutional solid solution strengthening. The enhanced plasticity is attributed to three synergistic mechanisms: (1) elimination of embrittling coarse oxide inclusions via oxygen reduction, (2) precipitation strengthening from solution-derived nanoscale Ti-rich phases, and (3) improved grain boundary cohesion due to suppressed oxygen segregation. These combined effects enable the alloy to retain high strength meanwhile achieving unprecedented ductility. Importantly, the nanoscale Ti-rich precipitates exhibit superior thermal stability, retaining their morphological integrity even after exposure to high-temperature environments. This characteristic further expands the alloy’s potential for high-temperature service scenarios.