Mechanical properties of tantalum with different types of microstructure under high-rate deformation

Abstract

The paper presents experimental data on the mechanical behavior of coarse-grained (80 μm) tantalum and cold-forged fine-grained (1–2 μm) tantalum under static, dynamic and shock wave loading. The data includes σ−ɛ compression diagrams for a strain rate of 10−3–103 s−1, impact velocity dependences of the relative change in cylinder length in Taylor impact tests, and time dependences of the free surface velocity in the Ta specimens under shock wave loading. It is found that the 80-fold decrease in Ta grain size only slightly affects the strength properties of the material under static and dynamic loading. Measurements of the free surface velocity under shock wave loading at ∼ 17 GPa point to a decrease in elastic precursor in the fine-grained tantalum by ∼35% and to an increase in its critical fracture stress by 15–20% compared to those in the coarse-grained tantalum. A complex strain rate dependence of the tantalum strength properties was revealed. The microstructure of the coarse-grained Ta specimens loaded at a shock wave pressure of 20–130 GPa for different times was examined, and the dislocation density and the number of shear bands formed under shock wave loading were measured.