Papers by Keyword: Biomedical Alloy

Abstract: This paper focuses on study of the kinetics and the mechanism of passive film formation on novel superelastic biomedical Ti-22Nb-6Ta and Ti-21.8Nb-6Zr (at.%) alloys in simulated physiological solutions using XPS and electrochemical techniques in comparison with commercially pure titanium and Nitinol. In vitro biocompatibility study of Ti-22Nb-6Ta alloy was carried out as well. Ti-22Nb-6Ta alloy manifests a strong trend to protective passive film formation during the first stage of oxidation in simulated physiological solutions. It is shown that Ti-22Nb-6Ta and Ti-21.8Nb-6Zr electrochemical characteristics are comparable to those of titanium and Nitinol, and the alloy can be recommended for use in implantology.

Abstract: Composition dependence of the compatibility condition at junction plane (JP) (interface between habit plane variants (HV)) was evaluated by geometrically non-linear theory of martensite in Ti-Nb-Al shape memory alloys that have β (cubic) to α” (C-orthorhombic) martensitic transformation. The kinematic compatibility (KC) condition requires non-zero rotation of HV to form compatible JP; the angle of this rotation is termed θ. This means that the invariant habit plane (HP) and the compatible JP are not formed simultaneously. It turned out that twelve types of θ exist depending on the pair of HV. Composition dependence of each type of θ was systematically investigated. The previous results of transmission electron microscopy observations were also discussed in terms of the present results.

Abstract: The self-accommodation microstructure of a -titanium shape memory alloy (SMA) was investigated by conventional transmission electron microscopy (CTEM) observation. There were two distinct minimum units for the self-accommodation microstructure. One was the V-shaped pair of two habit plane variants that were bounded by the {111}TypeI twin as reported in some previous studies. The other was the bundle of the two habit plane variants that were bounded by the <211>TypeII twin. The later one had not been recognized as the self-accommodation microstructure in -titanium SMAs.

Abstract: In order to produce new β (bcc) Ti alloys for medical applications, effects of Mn substitution for Cr on phase constitution and mechanical properties of Ti-Cr-Sn alloys were investigated. All the Ti-7mol%(Cr, Mn)-3mol%Sn alloys investigated by XRD analysis were identified as β (bcc) alloys, and athermal ω phase was also detected in Ti-7mol%Mn-3mol%Sn . The lattice parameter of β was slightly decreased by Mn substitution. Besides, the Mn substitution for Cr raised the hardness and the strength while reduced the ductility of the Ti-Cr-Sn alloys. The hardening by Mn substitution must be due to ω precipitation. The hardening is discussed from the viewpoint of electron atom ratio (e/a) in comparison with Ti-Cr binary alloys in the literature.

Abstract: An intensive amplitude arrangement for reciprocal tribocontact of biomedical alloys, Ag-20.0Pd-14.5Cu-12.0Au, Au-5.0Pt-2.0Pd-9.2Ag-15.0Cu and Ti-29Nb-13Ta-4.6Zr was conducted in order to check the details of friction and wear alterations around the transition from fretting to sliding. It is shown that the friction force exhibits stagnation for the Ag alloy and decrease for the Au alloy and the Ti alloy in certain domain of oscillating amplitude. Beyond the domain the friction force increases with the amplitude, and below the lower threshold and above the upper threshold triboevent is complete fretting and sliding respectively. Observation of friction-force waveform and SEM topography found, a hybrid mechanism of fretting and sliding is dominant in the amplitude domain, and the strong adhesion between the self-mated alloys is responsible to this exhibition.

Abstract: Anisotropy in elastic properties of Ti-24mol%Nb-3mol%Al (TiNbAl), a new biomedical shape memory alloy developed by our group, was characterized in a temperature range from 133K to 413K. A well developed <110>{112}-type recrystallization texture is formed by an annealing at 1273K for 1.8ks after a severe cold-rolling. Young’s modulus of the -phase exhibited a strong anisotropy depending on the loading direction. Young’s modulus along of -phase of TiNbAl around room temperature was estimated to be , with assuming that the texture is perfectly developed.