Structure, phase composition and mechanical properties in bioinert zirconium-based alloy after severe plastic deformation

Abstract

Bioinert Zr-1Nb alloy, which is a prospective material for the fabrication of implants for different applications, is studied. Annealed billets of the alloys are subjected to severe plastic deformation including multi-cycle abc-pressing and multipass rolling in grooved rolls. The abc-pressing stage involves three cycles of pressing within the temperature range 500 -400°C with one pressing in each cycle at a given temperature. In the second stage, the billets are deformed through rolling in grooved rolls at room temperature. Rolling in grooved rolls provided the formation of a homogeneous structure throughout the bulk billet volume and additional grain refinement. After annealing the alloy had a fine-grained structure consisting of 2.8 µm sized equiaxial α-Zr matrix grains and 0.4 µm sized β-Nb particles distributed on the boundaries and interiors of α-Zr matrix grains. As a result of severe plastic deformation, a binary ultrafine-grained alloy with 0.2 µm size of structural elements was obtained. Transmission electron microscopy shows that the microstructure of the alloy consists of α-Zr grains, while β-Nb phase grains are not identified structurally or via X-ray diffraction. Only the diffraction identification analysis reveals the presence of β-Nb in the alloy. Ultrafine-grained structure enhances the mechanical properties of the alloys: yield stress 450 MPa, ultimate tensile strength 780 MPa, and microhardness 2800 MPa are obtained while keeping a low value of Young's modulus (51 MPa) comparable to the Young's modulus of bone tissue.

Behavior of Zr–1Nb alloy in coarse- and ultrafine-grain states under laser-induced shock wave loading

“…This unique material was provided by the Laboratory of Physics of Nanostructured Biocomposites of the Institute of Strength Physics and Materials Science of the Siberian Branch of Russian Academy of Sciences. The method of obtaining, mechanical testing, as well as structural studies of this material are presented in detail in the works [45][46][47][48][49].…”

Analyzing the Deformation and Fracture of Bioinert Titanium, Zirconium and Niobium Alloys in Different Structural States by the Use of Infrared Thermography

“…In order to analyze the deformation behavior of alloys, we have used standard flat specimens manufactured in accordance with the Russian State Standard GOST 25.502, see Figure 1. The specimens were milled from 1.2 mm-thick strip-like blank parts of test alloys nanostructured by the SPD method [23] with the final sample thickness being 0.85 mm. For testing, we selected 17 specimens of titanium and Zr-1Nb alloy in the UFG state with the average size of structural elements (grains, sub-grains, fragments) of 0.2 µm and 21 specimens of Ti-45Nb alloy (average size of structural elements 0.3 µm).…”

“…This process did not affect the structure of UFG alloys but enhanced their plasticity due to diminished internal stresses. Eight specimens made of VT1-0 titanium and Zr-1Nb alloys, as well as 11 specimens made of Ti-45Nb alloy, were transited into the CG state by recrystallization annealing [23]. may be predicted based on an understanding of the microcrystalline structure of the UFG state.…”

“…This process did not affect the structure of UFG alloys but enhanced their plasticity due to diminished internal stresses. Eight specimens made of VT1-0 titanium and Zr-1Nb alloys, as well as 11 specimens made of Ti-45Nb alloy, were transited into the CG state by recrystallization annealing [23]. Tensile tests of the specimens were carried out on an Instron VHS 40/50-20 servo-hydraulic high-rate test system (Instron European Headquarters, High Wycombe, UK) servo-hydraulic test bench at a given constant strain rate of 0.005 s −1 .…”

Development of Ultrafine–Grained and Nanostructured Bioinert Alloys Based on Titanium, Zirconium and Niobium and Their Microstructure, Mechanical and Biological Properties

“…The structure of a zirconium alloy with such a range of grain sizes, according to the classification in [95], should be considered to be a small-grained (SG) state. The application of the combined SPD method, including MDF and MPGR, with further annealing at 300 • C, enhanced the formation of the UFG structure in the Zr-1Nb alloy [107][108][109].…”