Optimizing impact toughness of a α + β titanium alloys by tailoring the strength matching of α_p and β_t through heat treatment

Conventional α + β titanium alloys often exhibit inadequate impact toughness, significantly limiting their engineering applications under dynamic loading conditions. This study addresses this limitation by precisely controlling furnace cooling rates to optimize the bimodal microstructure of Ti-6Al-3Mo-4Sn-0.3Si (Ti634) alloy, achieving an exceptional balance between strength and toughness: yield strength of 943.1 MPa, ultimate tensile strength of 1022.7 MPa, elongation to failure of 17.6 %, and a significantly enhanced impact toughness of 58.0 J/cm². The remarkable improvement in impact toughness originates from the synergistic effect of nano-sized Ti₃Al precipitates in primary α (α_p) phase and lamellar secondary α (α_s) phase within transformed β (β_t) matrix, which reduces the mechanical mismatch between α_p phase and β_t matrix.