Effects of microstructure and alloy composition on hydroxyapatite precipitation on alkaline treated α/β titanium alloys.

The current work aims at exploring the effects of the microstructure and alloy composition on enhancing the bone osseointegration in Ti-6Al-4V (Ti64) and Ti-6Al-7Nb (Ti67) alloys. This was revealed by investigating the alloy susceptibility to grow hydroxyapatite (HA) on their surfaces after immersion in simulated body fluid (SBF). The specimens were produced by two methods: forging and casting in order to study the influence of the microstructure on the precipitation process. The surface conditions investigated were the polished, alkaline and the hydrothermally treated. It was found that precipitation on both of Ti64 and Ti67 occurs after about 4 weeks and considerably dissolve back with further immersion. Precipitation process is enhanced at some pH levels lower than the neutral level. Forged Ti67 has less reactivity with Hank solution than Ti64 specimens; the reverse is true for cast specimens. In case of the alkaline treated specimens, precipitations on cast specimens were denser than on the forged ones. For the hydrothermally treated specimens, high amounts of Ca and P were observed on cast Ti67 indicating that hydrothermal treatment is considered the best surface modification treatment for alloy Ti67.