Deciphering the microstructural evolution and adiabatic shearing behavior of the titanium alloy with stress-induced ω phase transformation during dynamic compression

Abstract

Metastable β titanium alloys are attracting great interest due to their intricate plastic deformation mechanisms. In this work, a novel metastable β titanium alloy Ti-6Mo-3.5Cr-1Zr is developed by controlling the phase stability. The alloy exhibits a compressive strength of ∼ 1152 MPa with large malleability (∼34 %) during dynamic compressions. The microstructural evolution and adiabatic shearing behavior of the alloy are investigated by applying stop rings to control the compressive strains. Microstructural characterizations and differential scanning calorimetry show that the content of stress-induced ω (SIω) phase increases with the accumulation of strain, resulting in strain hardening of the material. The formation of adiabatic shear band (ASB) is observed in samples with 30% strain, whilst the formation and expansion of ASB are hindered by stress-induced structures. The microstructural evolution along outer edge → transition zone → center of the ASB region corresponds to (β + ω)→(β + α)→(β), which is caused by the temperature increasement in ASB. In addition, the average grain sizes in ASB region are gradually refined under the action of dynamic recrystallization. These results provide insights into the dynamic deformation mechanism and adiabatic shearing behavior of metastable β titanium alloys.