Room-Temperature Deformation and Microstructure Changes in Ti-6Al-4V under High Strain Rates

This study examines the mechanical behavior and microstructural changes of Ti-6Al-4V alloy subjected to a broad spectrum of strain rates ranging from 0.001 to 4000 s⁻¹, employing uniaxial tensile testing alongside scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy characterization techniques. Under quasi-static loading conditions, the alloy demonstrates conventional strain hardening accompanied by stable ductile fracture mechanisms. With progressive increases in strain rate, a distinct secondary hardening stage emerges, attributed to localized deformation zones and heightened dislocation slip activity within the microstructure. Electron backscatter diffraction analysis reveals intensified α/β phase boundary interactions and a marked rise in geometrically necessary dislocation density, collectively facilitating dynamic recovery processes and the formation of ultra-fine subgrain structures. These microstructural mechanisms effectively retard necking onset and, counterintuitively, enhance tensile elongation to approximately 18% at a strain rate of 3828 s⁻¹. Fractographic examination further confirms a clear morphological transition from uniformly distributed dimple fracture patterns to layered delamination failure modes as strain rate escalates. Collectively, these results establish a comprehensive microstructural mechanics framework governing strain-rate-dependent plasticity in dual-phase titanium alloys. The insights derived from this investigation carry significant practical implications for the design and performance optimization of structural components used in aerospace, automotive, and defense sectors that routinely encounter dynamic and impact loading scenarios.