Deformation mechanism and mechanical properties of a thermomechanically processed β Ti–28Nb–35.4Zr alloy
Graphical abstract
Introduction
Metallic biomaterials have the oldest history when compared with other biomaterials (Niinomi, 2002), and stainless steels were the first metals used in orthopedics in 1926 (Nouri and Wen, 2015). Commercially pure titanium (CP-Ti) and titanium alloys are currently preferred as orthopedic implant materials due to their excellent biocompatibility (Geetha et al., 2009), high corrosion resistance (Niinomi, 1998), and relatively low Young's modulus (Long and Rack, 1998). Titanium alloys can be used as hip- and knee- joint prostheses, bone plates, screws, and nails for fractures in the field of orthopedics (Destefani, 1990). The superior mechanical, physical, and biological performances of CP-Ti and titanium alloys in comparison with other metallic materials play an important role in making them one of the most attractive materials for biomedical applications (Niinomi, 1998, Rack and Qazi, 2006). One of the most attractive β-type Ti alloys developed for biomedical applications is Ti-13 Nb-13Zr (wt%). The Ti-13Nb-13Zr alloy, developed by Davidson and Kovacs (Davidson and Kovacs, 1992), has been used for orthopedic and dental implant applications due to its mechanical and biological compatibilities (Davidson et al., 1994, Geetha et al., 2001). Ti-13Nb-13Zr showed a wide range of mechanical properties after various thermomechanical processes, with Young's modulus and yield strength being in the range of 79–84 GPa, and 836–908 MPa, respectively (Niinomi, 1998). New Ti-Nb-Zr alloys with different concentrations of niobium and zirconium for biomedical applications were also reported by different research groups and their Young's modulus and yield strength ranged from 59 to 75 GPa and 345–810 MPa, respectively (Ning et al., 2010, Ozan et al., 2015, Zhang et al., 2013).
The d-electron design method has been extensively used by researchers working on β and metastable β titanium alloys and their mechanical properties (Biesiekierski et al., 2016, Biesiekierski et al., 2017, Kuroda et al., 1998, Lin et al., 2016, Matsugi et al., 2010, Ozan et al., 2015, Saito et al., 2003, Zhang et al., 2011). Our previous studies (Lin et al., 2016, Ozan et al., 2015) have demonstrated that new β titanium alloys designed by using the delectron design method (Morinaga et al., 1988) combined with the molybdenum equivalence (Moeq) (Bania, 1994) and electron-to-atom ratio (e/a) (Boyer et al., 1994) approaches showed an excellent combination of mechanical properties for biomedical applications.
It is well known that thermomechanical processing, a metallurgical process that combines plastic deformation process such as cold rolling (CR) with a thermal process such as annealing, is widely used to change the microstructure of metallic materials to achieve the required mechanical properties for industrial applications (Elmay et al., 2013, Kim et al., 2006). Meanwhile, titanium alloys are not conventionally used in their as-cast condition; instead, they are used after thermomechanical processing which enhances their mechanical properties (Guo et al., 2015, Helth et al., 2017, Matsumoto et al., 2005, Yue et al., 2016). As such, cold rolling and annealing were performed on the newly developed β Ti–28Nb–35.4Zr alloy to investigate the microstructural evolution and mechanical properties of the alloy after thermomechanical processing in this study. To date, no study on the deformation mechanisms has been conducted on the new β type Ti–28Nb–35.4Zr alloy. It is unclear what deformation products would result from the various thermomechanical processes and how the deformation products would affect the mechanical properties of the alloy. As such, cold rolling at different reduction ratios and followed by annealing were performed on the newly developed titanium alloy to investigate the microstructural evolution and its effect on the mechanical properties of the alloy.
Section snippets
Materials preparation
A cold crucible levitation melting (CCLM) method, which presents an advantage in terms of enabling homogenous melting between alloying elements with large melting point differences (Matsugi et al., 2010), was used for the preparation of the as-cast alloy. An ingot with a nominal composition of Ti–28 Nb–35.4Zr (wt%, hereafter denoted Ti–Nb–Zr) was re-melted 5 times in order to guarantee chemical homogeneity. The as-cast Ti–Nb–Zr alloy ingot was subjected to solution treatment at 890 °C for 1 h to
Microstructural characterization
Fig. 2 shows the optical micrographs of the Ti–Nb–Zr alloy specimens after different thermomechanical processes. The grain size of the ST specimen was in the range of 500 ~ 600 µm; however, the CRST specimen showed recrystallized grains with grain size in the range of 50 ~ 150 µm after annealing. The grain size of the CRST specimen is significantly smaller compared to that of the ST specimen. Thin parallel lines, marked with white arrow, can be observed in the optical micrograph of CR-1 (Fig. 2
Conclusions
In this study, the effects of thermomechanical processes on the mechanical properties of a Ti–Nb–Zr alloy were investigated. The tensile strength of the alloy increased with an increase in the cold rolling ratio, whereas the ductility, i.e., the elongation at rupture decreased. The Ti–Nb–Zr alloy after cold rolling at a thickness reduction ratio of 86% followed by annealing exhibited lower Young's modulus than that of the cold rolled specimens, and yet retained high mechanical strength and
Acknowledgements
The authors acknowledge the financial support for this research by the National Health and Medical Research Council (NHMRC), Australia, through grant GNT1087290; and the Australian Research Council (ARC) through the discovery grant DP170102557. YL is also supported through an ARC Future Fellowship (FT160100252). The authors also acknowledge the scientific and technical assistance of RMMF (RMIT University’s Microscopy and Microanalysis Facility, a linked laboratory of the Australian Microscopy &
Competing financial interests statement
The authors declare that there are no conflicts of interest.
References (57)
- et al.
Biocompatibility of Ti-alloys for long-term implantation
J. Mech. Behav. Biomed. Mater.
(2013) - et al.
Investigations into Ti–(Nb,Ta)–Fe alloys for biomedical applications
Acta Biomater.
(2016) - et al.
Impact of ruthenium on mechanical properties, biological response and thermal processing of β-type Ti–Nb–Ru alloys
Acta Biomater.
(2017) - et al.
Chapter 1 - Properties of Materials, Biomaterials Science
(1996) - et al.
Effects of thermomechanical process on the microstructure and mechanical properties of a fully martensitic titanium-based biomedical alloy
J. Mech. Behav. Biomed. Mater.
(2013) - et al.
Ti based biomaterials, the ultimate choice for orthopaedic implants - a review
Progress Mater. Sci.
(2009) - et al.
Effect of thermomechanical processing on microstructure of a Ti–13Nb–13Zr alloy
J. Alloy. Compd.
(2001) - et al.
Effect of stress-induced α″ martensite on young's modulus of β Ti–33.6Nb–4Sn alloy
Mater. Sci. Eng.: A
(2013) - et al.
Effect of Zr and Sn on young's modulus and superelasticity of Ti–Nb-based alloys
Mater. Sci. Eng.: A
(2006) - et al.
Elastic deformation behaviour of Ti-24Nb-4Zr-7.9Sn for biomedical applications
Acta Biomater.
(2007)
Effect of thermomechanical processing on the mechanical biofunctionality of a low modulus Ti-40Nb alloy
J. Mech. Behav. Biomed. Mater.
Effect of thermo-mechanical treatment on mechanical properties and shape memory behavior of Ti–(26–28)at% Nb alloys
Mater. Sci. Eng.: A
Design and mechanical properties of new beta type titanium alloys for implant materials
Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process.
Deformation-induced changeable Young's modulus with high strength in β-type Ti–Cr–O alloys for spinal fixture
J. Mech. Behav. Biomed. Mater.
Titanium alloys in total joint replacement - a materials science perspective
Biomaterials
Microstructures and mechanical properties of metastable β TiNbSn alloys cold rolled and heat treated
J. Alloy. Compd.
Self-adjustment of Young's modulus in biomedical titanium alloys during orthopaedic operation
Mater. Lett.
Mechanical properties of biomedical titanium alloys
Mater. Sci. Eng. a-Struct. Mater. Prop. Microstruct. Process.
Development of Ti–Nb–Zr alloys with high elastic admissible strain for temporary orthopedic devices
Acta Biomater.
New Ti-Ta-Zr-Nb alloys with ultrahigh strength for potential orthopedic implant applications
J. Mech. Behav. Biomed. Mater.
Titanium alloys for biomedical applications
Mater. Sci. Eng.: C.
Theoretical study of the effects of alloying elements on the strength and modulus of beta-type bio-titanium alloys
Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process.
The use of titanium for medical applications in the USA
Mater. Sci. Eng.: A
Thermomechanical processing of beta titanium alloys - an overview
Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process.
Evolution of deformation mechanisms of Ti-22.4Nb-0.73Ta-2Zr-1.34O alloy during straining
Acta Mater.
Enhanced mechanical properties for mill-annealed Ti-20Zr-6.5Al-4V alloy with a fine equiaxed microstructure
Mater. Sci. Eng.: A
Shape memory and superelastic behavior of Ti–7.5Nb–4Mo–1Sn alloy
Mater. Des.
Influence of equiatomic Zr/Nb substitution on superelastic behavior of Ti–Nb–Zr alloy
Mater. Sci. Eng.: A
Cited by (77)
Stability and growth kinetics of {112} twin embryos in β-Ti alloys
2024, Acta MaterialiaExceptional strength-plasticity synergy in β-Ti alloy via HPT and short-period annealing
2023, Journal of Alloys and Compounds