prismatic, basal, and slip strengths of commercially pure Zr by micro-cantilever tests

Slip strengths of <a> basal, <a> prism, and <c+a> pyramidal systems in commercially pure zirconium have been determined using micro-cantilever testing. A range of single crystal cantilevers 0.5 µm to 10 µm wide, oriented for single slip were prepared using focused ion beam (FIB) machining and subsequently deflected using a nanoindenter. The critical resolved shear stress (τcrss) was found by fitting a crystal plasticity finite element model to the experimental load-displacement data for these micro-bending tests. All the three slip systems in alpha-Zr show a marked size effect in bending described well by CRSS(W)=Tau0 + AWn, where W is the cantilever width, Tau0 is the CRSS at the macro scale and n=-1. The exponent, n, of near -1 is in good accord with hardening caused by the back stress generated by dislocations piling up at a diffuse barrier caused by the reduction of stress near the neutral axis. The macro scale CRSS values were used to successfully simulate deformation of a conventional macroscopic compression test.