Sintering of Titanium Hydride Powder Compaction

Sintering by the TiH2 and Ti powder compaction was performed at 1423∼1623K for 2hours at 1.33x10-3Pa. The sinter-ability of TiH2 powder was higher than that of pure titanium powder, leading to near 99% of relative density, which was the competing level with that by HIP process. In the direct sintering of TiH2 powder compaction, the interstitial hydrogen atoms was released before sintering through the grain boundaries and meet the titanium oxide phase existing in the grain boundaries as the film forms. We found thermodynamically there that the hydrogen atoms could effectively reduce the titanium oxide existing on the powder surfaces or grain boundaries with a considerable driving force of about -250 kJ/mole. Such a self-reduction process by hydrogen atoms makes the grain boundaries very clean with oxide-free condition and helpful for sintering. Moreover, the de-hydrogenated titanium regions near grain boundaries could become unstable due to the formation of many vacancy defects by the release of hydrogen and also evoke the sintering ability.