High-strain rate behavior of nanostructured niobium processed by severe plastic deformation to very large strains

In this work, we have investigated the high-strain rate, uni-axial compressive behavior of nanostructured niobium (Nb), a refractory metal with body-centered cubic (bcc) lattice structure. The material was processed by equal channel angular extrusion (ECAE) to a maximum of 24 passes via route E. The microstructure of the processed billets was analyzed using electron back-scattering diffraction (EBSD). Microstructural analysis including grain size and texture studies showed the resultant microstructure to be nanocrystalline (< 400 nm) and of homogeneous texture after 24 passes. To examine the mechanical properties of the ECAE-nanostructured Nb, mechanical testing within a wide range of strain rates from quasi-static loading (strain rate <1.0 s-1) to high rate (strain rate > 103 s-1) loading was performed. Nanostructured Nb was observed to exhibit homogenous plastic flow, with only minor and diffuse adiabatic shear localization under high-rate uni-axial compression. Flow softening is primarily caused by uniform adiabatic temperature rise of the whole specimen combined with such diffuse shear localization.

Proceedings of the 8th International Conference on Tungsten, Refractory and Hardmaterials

Pan, Z., Ying, W., Wei, Q., Xu, F., Zhang, X., Hartwig, K. T., Kecskes, L., & Mathaudhu, S

High-strain rate behavior of nanostructured niobium processed by severe plastic deformation to very large strains Conference Paper