Nag S, Banerjee R, Stechschulte J, Fraser H L
Center for the Accelerated Maturation of Materials, Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio, USA.
J Mater Sci Mater Med. 2005 Jul;16(7):679-85. doi: 10.1007/s10856-005-2540-6.
The microstructural evolution and attendant strengthening mechanisms in two biocompatible alloy systems, the binary Ti-15Mo and the quaternary Ti-13Mo-7Zr-3Fe (TMZF), have been compared and contrasted in this paper. In the homogenized condition, while the Ti-15Mo alloy exhibited a single phase microstructure consisting of large beta grains, the TMZF alloy 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 h, both alloys exhibited the precipitation of refined scale secondary alpha precipitates homogeneously in the beta matrix. However, while the hardness of the TMZF alloy marginally increased, that of the Ti-15Mo 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 in the homogenized and homogenized plus aged conditions. The results indicate that the omega precipitates dissolve on ageing in case of the Ti-15Mo alloy, consequently leading to a substantial decrease in the hardness. In contrast, the omega precipitates do not dissolve on ageing in the TMZF alloy and the precipitation of the fine scale secondary alpha leads to increased hardness.
本文对两种生物相容性合金体系——二元Ti-15Mo和四元Ti-13Mo-7Zr-3Fe（TMZF）的微观结构演变及相应的强化机制进行了比较和对比。在均匀化状态下，Ti-15Mo合金呈现出由粗大β晶粒组成的单相微观结构，而TMZF合金的微观结构主要由具有晶界α析出物的β基体和低体积分数的晶内α析出物组成。在600℃对均匀化合金进行4小时时效处理后，两种合金均在β基体中均匀析出了细化的片状二次α析出物。然而，时效处理后，TMZF合金的硬度略有增加，而Ti-15Mo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，对两种合金在均匀化状态以及均匀化加时效状态下进行了透射电子显微镜（TEM）研究。结果表明，在Ti-15Mo合金中，ω析出物在时效过程中溶解，从而导致硬度大幅下降。相反，在TMZF合金中，ω析出物在时效过程中不溶解，并且细小片状二次α的析出导致硬度增加。
