2002 Volume 43 Issue 12 Pages 2964-2969
The effects of several commonly used heat treatment schemes on the microstructures of two Ti–Nb–Ta–Zr alloys aimed at biomedical applications were studied in this work using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The specimens were water quenched from 790°C and then aged at temperatures between 300°C and 600°C. The experimental results showed that α and ω phase precipitated from the metastable β matrix in Ti–29Nb–13Ta–4.6Zr alloy during isothermal ageing. But for Ti–39Nb–13Ta–4.6Zr, the precipitation reaction was more sluggish than that in Ti–29Nb–13Ta–4.6Zr because of high amount of β stabilizing elements in the former alloy. As a result the α phase was unable to precipitate during short time ageing treatment. After longer time (12 days) ageing treatment at 500°C or 400°C, recognizable α precipitates were observed in the aged samples. It is concluded that Ti–29Nb–13Ta–4.6Zr can be heat treated to obtain different microstructures and is better than Ti–39Nb–13Ta–4.6Zr in terms of age hardenability.
