Novel Zr-Rich Alloys of Ternary Ti-Zr-Nb System with Large Superelastic Recovery Strain

Abstract

Four novel superelastic alloys, Ti-41Zr-12Nb, Ti-42Zr-11Nb, Ti-43Zr-10Nb, Ti-44Zr-10Nb (at.%), were obtained and studied in terms of their microstructure and mechanical properties. The obtained alloys were subjected to thermomechanical treatment, providing alloys with a pronounced superelastic behavior. Materials phase composition and microstructure were studied using XRD and SEM methods. Based on the XRD results, maximum lattice strains in the [011]β direction were calculated as 5.9%, 6.3%, 7.5%, and 7.2% for Ti-41Zr-12Nb, Ti-42Zr-11Nb, Ti-43Zr-10Nb, and Ti-44Zr-10Nb alloys, respectively. Mechanical properties of the thermomechanically-treated alloys were studied by Vickers microhardness testing, static tensile testing, and superelastic mechanical cycling. The maximum superelastic recovery strains attained at room temperature was 3.7%, 1.9%, 3.2%, and 3.0% for the Ti-41Zr-12Nb, Ti-42Zr-11Nb, Ti-43Zr-10Nb, and Ti-44Zr-10Nb alloys, respectively. Ti-41Zr-12Nb alloy demonstrated the highest ductility, with relative elongation to failure of over 20%, combined with the total recovery strain of more than 6%. Obtained results indicate that Ti-41Zr-12Nb is one the most promising alloys of the Ti-Zr-Nb system, with quite perfect superelastic behavior at room temperature.

A review on β-Ti alloys for biomedical applications: The influence of alloy composition and thermomechanical processing on mechanical properties, phase composition, and microstructure

“…MPa was obtained for Ti-41Nb-12Zr and Ti-44Nb-10Zr. 179 Ozan et al studied Ti-Nb-Zr ternary system with 24.8-34 wt% of Nb and 25-40.7 wt% of Zr. All the alloys consisted of β-phase with equiaxed microstructure.…”

Effect of Cooling and Annealing Conditions on the Microstructure, Mechanical and Superelastic Behavior of a Rotary Forged Ti–18Zr–15Nb (at. %) Bar Stock for Spinal Implants

“…% Zr) with maximum theoretical recovery strains of ~6% and 7%, respectively. In Figure 12 and Table 2 , the mechanical and functional properties of the Ti–Zr–Nb-based alloys provided in [ 29 , 31 , 33 , 34 , 40 , 42 , 60 , 61 , 62 ] are compared with those obtained in this work.…”

“… Comparison of the strength ( UTS ) and superelasticity ( ε r se max , ε β↔α max , ε r se max /ε β↔α max ) characteristics of the studied and reference alloys [ 29 , 31 , 33 , 34 , 40 , 42 , 60 , 61 , 62 ]. …”

“…It must, however, be noted that these quaternary alloys are difficult to produce on an industrial scale because of large differences in the melting temperatures of the alloy components. In this context, ternary Ti–Zr–Nb alloys with an advantageous combination of strength and ductility, low Young’s modulus (<50 GPa) and superelastic behavior resulting from stress-induced reversible β↔α ″ martensitic transformation with a maximum theoretical superelastic recovery strain as high as ~6% [ 39 , 40 , 41 , 42 ] appear to be less expensive, but promising, alternative implant materials.…”

“…To improve the mechanical and functional properties of β -type SMAs, such as Ti–Zr–Nb, their microstructure, phase composition and texture can be controlled by thermomechanical treatments (TMTs), which typically include cold rolling (CR) and post-deformation annealing (PDA) [ 23 , 24 , 25 , 27 , 29 , 30 , 32 , 33 , 34 , 40 , 41 , 42 , 43 ]. In most of the mentioned works, severe CR with high accumulated true strains ( e ≥ 3.0) was applied [ 23 , 24 , 25 , 27 , 29 , 30 , 32 , 34 , 40 ] and PDA was carried out in vacuum furnaces.…”