Intra-granular alpha precipitation in Ti–Nb–Zr–Ta biomedical alloys
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This article investigates the intra-granular precipitation of nanometer-scale α platelets in the β matrix of a complex quaternary β titanium alloy, Ti-35Nb-7Zr-5Ta (all in wt%), for orthopedic implant applications, during β-solutionizing/quenching/aging type heat-treatments. The role of metastable ω precipitates on the nucleation and growth of these α precipitates, has been specifically addressed by coupling transmission electron microscopy (TEM) and 3D atom probe (3DAP) tomography studies on this alloy. Athermal ω precipitates form in this alloy on quenching from above the β-transus temperature. On isothermal annealing at low temperatures (~400 °C), these ω precipitates coarsen, rejecting Zr into the adjacent β matrix as determined by 3DAP studies. Concurrently, the nucleation and growth of α precipitates is initiated at or near the ω/β interfaces, as determined by TEM studies. In addition to coherency strains induced by the ω precipitates, the local enrichment of Zr adjacent to these precipitates appears to play an important role in aiding the nucleation and growth of Zr-rich α precipitates in this alloy.
KeywordsTransmission Electron Microscopy Study Select Area Diffraction Pattern Coherency Strain Heterogeneous Nucleation Site Potent Nucleation Site
This work has been supported in part by the U. S. Air Force Office of Scientific Research (AFOSR), the National Science Foundation (NSF), and, the Center for the Accelerated Maturation of Materials (CAMM) at the Ohio State University.
- 9.Duerig TW, Williams JC (1984) Beta Titanium alloys in the 80’s: proceedings of the symposium. Atlanta, GA, United States, pp 19–67Google Scholar
- 10.Blackburn MJ, Williams JC (1968) Trans Met Soc AIME 242:2461Google Scholar
- 11.Pennock GM, Flower HM, West DRF (1980) Titanium ‘80: science and technology, pp 1343–1351Google Scholar
- 18.Hickman BS (1968) J Inst Met 96:330Google Scholar