Effect of Hydrogen on the Deformation Behavior and Localization of Plastic Deformation of the Ultrafine-Grained Zr–1Nb Alloy

Ekaterina Stepanova,Ivan Mishin,Maxim Syrtanov,Galina Grabovetskaya

doi:10.3390/met10050592

Abstract

In this paper, comparison studies of the hydrogen effect on the structural and phase state, deformation behavior, and mechanical properties of the fine- (average grain size 4 µm) and ultrafine-grained (average element size 0.3 and 0.4 µm) Zr–1wt.%Nb (hereinafter Zr–1Nb) alloy under tension at temperatures in the range of 293–873 K were conducted. The formation of an ultrafine-grained structure is established to increase the strength characteristics of the Zr–1Nb alloy by a factor of 1.5–2 with a simultaneous reduction of its resistance to the localization of plastic deformation at the macro level and the value of deformation to failure. The presence of hydrogen in the Zr–1Nb alloy in the form of a solid solution and hydride precipitates increases its resistance to the localization of plastic deformation at the macro level if the alloy has an ultrafine-grained structure and decreases if the structure of the alloy is fine-grained. In the studied temperature range, the Zr–1Nb alloy in the ultrafine-grained state has a higher resistance to hydrogen embrittlement than the alloy in the fine-grained state.

Highlights

Zirconium alloys are structural materials for core elements of nuclear power reactors due to their low neutron capture cross-section, high melting temperature, high and stable corrosion resistance in water, steam and other aggressive media, good plasticity, and high strength characteristics [1,2,3].the strength characteristics of these alloys are insufficient for operation upon exposure to radiation
All of the most widespread methods of UFG structure formation in metallic materials are based on severe plastic deformation (SPD) [9,10,11]
The σ0.2 values of the UFG Zr–1Nb–0.33H alloy differ slightly from the corresponding values for the FG Zr–1Nb–0.33H alloy. These results indicate a higher resistance to hydrogen embrittlement of the Zr–1Nb alloy in the UFG state in comparison with the FG state

Summary

Introduction

Zirconium alloys are structural materials for core elements of nuclear power reactors due to their low neutron capture cross-section, high melting temperature, high and stable corrosion resistance in water, steam and other aggressive media, good plasticity, and high strength characteristics [1,2,3].the strength characteristics of these alloys are insufficient for operation upon exposure to radiation. Zirconium alloys are structural materials for core elements of nuclear power reactors due to their low neutron capture cross-section, high melting temperature, high and stable corrosion resistance in water, steam and other aggressive media, good plasticity, and high strength characteristics [1,2,3]. The rate of hydrogen absorption by metallic materials is known to be increased when the grain sizes decrease [19,20,21,22]. This fact is critical for zirconium products of water-cooled nuclear power reactor cores, actively undergoing hydrogenation during operation [23,24]

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Discussion

Conclusion