Banerjee Rajarshi, Nag Soumya, Stechschulte John, Fraser Hamish L
Department of Materials Science and Engineering, The Ohio State University, 477 Watts Hall, 2041 College Road, Columbus, OH 43210, USA.
Biomaterials. 2004 Aug;25(17):3413-9. doi: 10.1016/j.biomaterials.2003.10.041.
The microstructural evolution and attendant strengthening mechanisms in two novel orthopaedic alloy systems, Ti-Nb-Zr-Ta and Ti-Mo-Zr-Fe, have been compared and contrasted in this paper. Specifically, the alloy compositions considered are Ti-34Nb-9Zr-8Ta and Ti-13Mo-7Zr-3Fe. In the homogenized condition, both alloys exhibited a microstructure consisting primarily of a beta matrix with grain boundary alpha precipitates and a low-volume fraction of intra-granular alpha precipitates. On ageing the homogenized alloys at 600 degrees C for 4 hr, both alloys exhibited the precipitation of refined scale secondary alpha precipitates homogeneously in the beta matrix. However, while the hardness of the Ti-Mo-Zr-Fe alloy marginally increased, that of the Ti-Nb-Zr-Ta alloy decreased substantially as a result of the ageing treatment. In order to understand this difference in the mechanical properties after ageing, TEM studies have been carried out on both alloys prior to and post the ageing treatment. The results indicate the existence of a metastable B2 ordering in the Ti-Nb-Zr-Ta alloy in the homogenized condition which is destroyed by the ageing treatment, consequently leading to a decrease in the hardness.
本文对两种新型骨科合金体系Ti-Nb-Zr-Ta和Ti-Mo-Zr-Fe的微观结构演变及相应的强化机制进行了比较和对比。具体而言，所考虑的合金成分分别为Ti-34Nb-9Zr-8Ta和Ti-13Mo-7Zr-3Fe。在均匀化状态下，两种合金的微观结构主要由β基体、晶界α析出物和少量的晶内α析出物组成。将均匀化后的合金在600℃时效4小时后，两种合金均在β基体中均匀析出了细小的片状二次α析出物。然而，时效处理后，Ti-Mo-Zr-Fe合金的硬度略有增加，而Ti-Nb-Zr-Ta合金的硬度则大幅下降。为了理解时效后力学性能的这种差异，对两种合金在时效处理前后都进行了透射电子显微镜（TEM）研究。结果表明，Ti-Nb-Zr-Ta合金在均匀化状态下存在亚稳的B2有序结构，时效处理会破坏这种结构，从而导致硬度下降。
