Dehydrogenation of nanocrystalline TiH2 and consequent consolidation to form dense Ti

Abstract

Dehydrogenation of nanocrystalline TiH 2 , produced by pulverization of commercially available powder, has been examined in detail by a combination of thermal analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The dehydrogenation to form Ti occurs as a two-step process involving the formation of an intermediate phase, TiH. In-situ experiments on dehydrogenation inside a transmission electron microscope reveal the possibility of a powder-metallurgy process for consolidation of Ti components by vacuum annealing of nanocrystalline TiH 2 at ϳ0.5T m , where T m is the melting point of Ti. Near-full densification of Ti has been achieved by sintering nanocrystalline TiH 2 under vacuum at ϳ0.5T m .

Some Effects of Particle Size on the Sintering of Titanium and a Master Sintering Curve Model

“…The latter was determined from a least-squares fit of the data for only the CERAC -100 sieve fractions to a log-linear densification curve, using Eq. [8]. The same value of m produced a reasonable fit for the CERAC -325 powder and the AEE <20-lm powders but not for the Sumitomo -100 powder.…”

“…[32] However, for the current data on titanium, Eq. [8] proves to be adequate for empirical modeling. We further extend the master sintering curve approach by assuming that a master densification curve exists for a particular powder, unaffected by compaction pressure.…”

“…[5] and [8]. Dilatometry curves for the CERAC -100 Ti powder were obtained for a compact sintered at 1400°C for 2 hours and for another compact sintered at 1200°C for 2 hours and then given a second treatment at 1200°C.…”

“…[18] Alternatively, they may be deliberately milled to an extremely small size. [8] In the latter case, almost full density was achieved after sintering at only 750°C.…”

An in situ Study of NiTi Powder Sintering Using Neutron Diffraction

“…However, it should be noted that the ex-situ XRD and TEM investigations may suffer from instant information loss in terms of the phase transformation during the heating process [19,27,30,46,47]. Additionally, although in situ high temperature XRD and X-ray synchrotron/neutron diffraction techniques were applied, their results may still be of concern.…”