Effect of high strain rates and different orientations on tensile behavior and microcosmic evolution of Ti-6Al-4V sheet

Abstract

Mechanical properties of titanium alloy (Ti-6Al-4V) sheet exhibit anisotropy under various strain rates. The split hopkinson tension bar (SHTB) tests were performed with Ti-6Al-4V sheet orientations under strain rates of 1500 s−1, 2500 s−1 and 3500 s−1. The microstructures and dynamic properties were obtained of Ti-6Al-4V sheet. Notable anisotropy was observed in all three kinds of high strain rates loading and all five orientations (0°(Rolling direction: RD), 30°, 45°, 60° and 90°(Transverse direction: TD)). The anisotropy of mechanical properties was quantitatively expressed by introducing plane anisotropy index (IPA). The mechanical properties (tensile strength) were greatly enhanced with the occurred recrystallization at different orientations and high strain rates. Ductile fracture was detected under the high strain rate, and the dimple size and depth varied at different orientations. The void defects were occurred which resulting in the macroscopic flow stress decreases sharply at the fracture stage. Finally, the relationship between mechanical properties and microstructure was also analyzed in detail.