Effects of phase constitution on magnetic susceptibility and mechanical properties of Zr-rich Zr-Mo alloys

Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan.
Acta biomaterialia (Impact Factor: 6.03). 07/2011; 7(12):4259-66. DOI: 10.1016/j.actbio.2011.07.005
Source: PubMed


The effects of the microstructures and phases of Zr-rich Mo alloys on their magnetic susceptibilities and mechanical properties were investigated in order to develop a Zr alloy with low magnetic susceptibility for use in magnetic resonance imaging (MRI). The magnetic susceptibility was measured with a magnetic susceptibility balance, while mechanical properties were evaluated by a tensile test. The microstructure was evaluated with an X-ray diffractometer, an optical microscope, and a transmission electron microscope. Evaluation of the microstructures revealed that the α' phase was the dominant form at less than 2% Mo content in the as-cast alloy. The ω phase was formed in as-cast Zr-3Mo but disappeared with aging at 973 K. Magnetic susceptibility was reflected in the phase constitution: the susceptibility showed a local minimum at Zr-(0.5-1)Mo with mostly α' phase and a minimum at Zr-3Mo with mostly β and ω phases. The magnetic susceptibility of as-cast Zr-3Mo increased at 973 K due to disappearance of the ω phase. However, the susceptibility was still as low as that of as-cast Zr-1Mo. The ultimate tensile strength of α'-based Zr-Mo alloys was tailored from 674 to 970 MPa, and the corresponding elongation varied from 11.1% to 2.9%. Because Zr-Mo alloys containing ω phase were found, through tensile tests, to be brittle this phase should be avoided, irrespective of the low magnetic susceptibility, in order to maintain mechanical reliability. Elongation of the Zr-3Mo alloy was dramatically improved when the phase constitution was changed to α and β phases by aging at 973 K for 86.4 ks. The magnetic susceptibilities of the α'-based Zr-Mo alloys are one-third those of Ti-6Al-4V and Ti-6Al-7Nb, and thus these Zr alloys are useful for medical devices under MRI.

8 Reads
  • Source
    • "al., 2003). Metals become magnetized when exposed to the high static magnetic field of an MRI machine and field inhomogeneity is induced as a result of the newly created magnetic field around the metallic dental devices. This inhomogeneity generates artifacts that then inhibit the precision of MRI diagnosis (Cortes et al., 2015; Hong et al., 2014; Suyalatu. et al., 2011). The size of the area that is affected by the artifacts is related to the magnetic susceptibility of the metals and decreases with decreasing magnetic susceptibility (Imai et al., 2013)."
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to investigate the bond strength of dental porcelain and the preheated Zr-14Nb alloy, and compare this strength with that of titanium. White oxide layers, which were predominantly composed of monoclinic zirconia, were formed on the preheated sample groups, and exhibited a greater roughness than the control samples. At the metal-ceramic interface, a greater Nb diffusion range was observed than in the control samples. The bond strengths of the samples subjected to 20min preheating treatment were the lowest (33.6±3.2MPa), which may be ascribed to the formation of a brittle thick oxide layer under excessive heat treatment. The samples subjected to this heat treatment for 5min exhibited the highest mean bond strength (43.7±5.9MPa), which was significantly higher than that of titanium (35.3±3.5MPa). Thus, the Zr-14Nb alloy is a promising candidate for fixed dental prosthesis, as long as the appropriate treatment conditions are adopted. Copyright © 2015 Elsevier Ltd. All rights reserved.
    08/2015; 53:131-141. DOI:10.1016/j.jmbbm.2015.08.008
  • [Show abstract] [Hide abstract]
    ABSTRACT: Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation. Recent advances in orthobiologics are proving interesting as well. This paper thus deals with the latest improvements being made to the existing implant materials and includes new materials being introduced in the field of biomaterials. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
    Journal of Biomedical Materials Research Part A 06/2012; 101(11):NA. DOI:10.1002/jbm.a.34605 · 3.37 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: New low modulus β-type titanium alloys for biomedical applications are still currently being developed. Strong and enduring β-type titanium alloy with a low Young's modulus are being investigated. A low modulus has been proved to be effective in inhibiting bone atrophy, leading to good bone remodeling in a bone fracture model in the rabbit tibia. Very recently β-type titanium alloys with a self-tunable modulus have been proposed for the construction of removable implants. Nickel-free low modulus β-type titanium alloys showing shape memory and super elastic behavior are also currently being developed. Nickel-free stainless steel and cobalt-chromium alloys for biomedical applications are receiving attention as well. Newly developed zirconium-based alloys for biomedical applications are proving very interesting. Magnesium-based or iron-based biodegradable biomaterials are under development. Further, tantalum, and niobium and its alloys are being investigated for biomedical applications. The development of new metallic alloys for biomedical applications is described in this paper.
    Acta biomaterialia 07/2012; 8(11):3888-903. DOI:10.1016/j.actbio.2012.06.037 · 6.03 Impact Factor
Show more