材料期刊网

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 790degreesC and then aged at temperatures between 300degreesC and 600degreesC. The experimental results showed that alpha and omega phase precipitated from the metastable beta 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 beta stabilizing elements in the former alloy. As a result the a phase was unable to precipitate during short time ageing treatment. After longer time (12 days) ageing treatment at 500degreesC or 400degreesC, recognizable a 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.