〈a〉 Prismatic, 〈a〉 basal, and 〈c+a〉 slip strengths of commercially pure Zr by micro-cantilever tests

Fionn P.E Dunne,T Benjamin Britton,Mitchell A Cuddihy,Angus J Wilkinson,Jicheng Gong

doi:10.1016/j.actamat.2015.06.020

Fionn P.E Dunne, T Benjamin Britton + Show 3 more

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https://doi.org/10.1016/j.actamat.2015.06.020

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Journal: Acta Materialia	Publication Date: Jun 24, 2015
Citations: 148	License type: cc-by

Affiliation: Imperial College London, University of Oxford

Abstract

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 0.5μm to 10μm 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 α-Zr show a marked size effect in bending described well by τCRSS(W)=τ0+AWn, where W is the cantilever width, τ0 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.

Highlights

Zirconium is widely used in the nuclear industry as nuclear fuel rod cladding in water reactors, due to its low neutron cross section, good corrosion resistance and reasonable mechanical properties
With the scaling exponent forced to À1, we find the constant A which represents the strength of the size effect to be 300 ± 30 Pa m for hai prism, 311 ± 66 Pa m for hai basal, 413 ± 55 Pa m for hc+ai slip, where the error bars indicate a 95% confidence interval
The hai prism, hai basal, and hc+ai on the first order pyramidal plane slip systems of commercial pure a-Zirconium were selectively investigated by testing particular crystal orientations using various sizes of micro-cantilever tests

Summary

Introduction

Zirconium is widely used in the nuclear industry as nuclear fuel rod cladding in water reactors, due to its low neutron cross section, good corrosion resistance and reasonable mechanical properties. To provide an adequate safety case and ensure safety during operation and shutdown, the mechanical performance of these polycrystalline components must be well known. Zirconium alloys for this application typically contain predominately the a-Zr (hcp) phase which exhibits pronounced anisotropy in both its elastic and plastic properties at the single crystal level. Design and operation of a reactor must involve selection of appropriate materials, processing routes and textures to provide adequate strength for in-service operation One such property is the critical resolved shear stress (CRSS) which describes the critical stress for plastic deformation to occur on a given slip system

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