Chaves J M, Florêncio O, Silva P S, Marques P W B, Afonso C R M
Department of Physics, UFSCar, C.P. 676, CEP 13565-905, São Carlos-SP, Brazil.
Department of Physics, UFSCar, C.P. 676, CEP 13565-905, São Carlos-SP, Brazil.
J Mech Behav Biomed Mater. 2015 Jun;46:184-96. doi: 10.1016/j.jmbbm.2015.02.030. Epub 2015 Mar 6.
Recent studies in materials for biomedical applications have focused on β-titanium alloys that are highly biocompatible, free of toxic elements and with an elastic modulus close to that of human bone (10-40 GPa). Beta Ti-xNb-3Fe (x=10, 15, 20 and 25 wt%) alloys were obtained by rapid solidification and characterized by anelastic relaxation measurements at temperatures between 140 K and 770 K, using a free-decay elastometer, as well as analysis by Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The observed stabilization of the β-phase with rising Nb content was linked to the strength of the relaxation peak around 570 K. The phase transformations detected in the anelastic relaxation spectra agreed with those observed in the DSC curves. However, the results from anelastic relaxation spectra provide more detailed information about the kinetics of phase transformations. At temperatures between 140 K and 300 K, there was an indication of a reversible transformation in the alloys studied. The elastic modulus measurements showed a hardening of the material, between 400 K and 620 K, related to the ω-phase precipitation. However, the starting temperature of ω-phase precipitation was clearly influenced by the Nb content, showing a shift to high temperature with increasing percentage of Nb. At temperatures above 620 K, a fall was observed in the dynamical elastic modulus, accompanied by a relaxation peak centered at 660 K, which was attributed to the growing α-phase arising from the ω-phase, which acts as a nucleation sites or from the decomposition of the metastable β-phase. XRD patterns confirmed the formation of β, α and ω phases after mechanical relaxation measurements. A predominant β phase with dendritic morphology was observed, which became more stable with 25 wt% Nb. The lowest elastic modulus was of 65 GPa obtained in the Ti-25Nb-3Fe alloy, representing a good low value for a β-Ti alloy with a relatively low addition of β stabilizing elements (Nb and Fe).
近期关于生物医学应用材料的研究聚焦于β钛合金，这类合金具有高度生物相容性、无有毒元素且弹性模量接近人体骨骼（10 - 40吉帕）。通过快速凝固获得了β-Ti-xNb-3Fe（x = 10、15、20和25重量%）合金，并使用自由衰减弹性计在140 K至770 K温度下通过滞弹性弛豫测量进行表征，同时进行差示扫描量热法（DSC）、X射线衍射（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）分析。观察到随着Nb含量增加β相的稳定化与570 K左右弛豫峰的强度有关。滞弹性弛豫谱中检测到的相变与DSC曲线中观察到的相变一致。然而，滞弹性弛豫谱的结果提供了关于相变动力学更详细的信息。在140 K至300 K温度之间，所研究的合金有可逆转变的迹象。弹性模量测量表明，在400 K至620 K之间材料发生硬化，这与ω相析出有关。然而，ω相析出的起始温度明显受Nb含量影响，随着Nb百分比增加向高温偏移。在620 K以上温度，观察到动态弹性模量下降，同时伴有一个以660 K为中心的弛豫峰，这归因于由ω相产生的α相增多，ω相充当形核位置或亚稳β相的分解。XRD图谱证实了机械弛豫测量后β、α和ω相的形成。观察到一种具有树枝状形态的主要β相，当Nb含量为25重量%时变得更稳定。在Ti-25Nb-3Fe合金中获得的最低弹性模量为65吉帕，对于添加相对较少β稳定元素（Nb和Fe）的β-Ti合金来说，这是一个不错的低值。
