Analysis of Deformation Mechanism Behaviors of Ti-5Mo-1Fe Alloy under Quasi-static and Dynamic Deformation

To evaluate the deformation mechanisms of Ti-5Mo-1Fe alloy, compression tests were performed at strain rates ranging from 10-3/sec to 3×103/sec at room temperature. The results showed that Ti-5Mo-1Fe alloy exhibited different deformation mechanisms depending on the strain rate. Under quasi-static strain rates, the Stress-Induced Martensitic (SIM) transformation from the metastable β phase (BCC) to the α" phase was observed through the double yield phenomenon in the stress-strain curve. This contributed to enhanced compressive strength, work hardening, and ductility by absorbing and dispersing deformation energy. Shear bands (SB) were observed near the fracture zone under quasi-static conditions, since the SIM transformation acts as an obstacle to dislocation movement. In contrast, a dynamic strain rate generated adiabatic shear bands (ASB) due to localized heating, leading to coarsened grains near the fracture zone. With increasing strain rates, significant temperature rises were detected in the specimens, leading to increased β phase stability and a reduced chemical driving force for the α" transformation, thereby suppressing the SIM transformation. Consequently, dislocation slip became the dominant deformation mechanism at high strain rates. This study provides insights into the strain rate sensitivity of metastable β-titanium alloys, offering fundamental information for the development of advanced Ti alloys with high strength, good ductility, and impact resistance.