Production and characterization of fully dense hydrogenated γ-TiAl by blended elemental approach

Fully dense nanocrystalline γ-TiAl alloys were produced by mechanical alloying (MA) of elemental titanium and aluminum powders in a high-energy ball mill for sixteen hours followed by hot isostatic pressing (HIP'ing) at 850°C or 1050°C and a 207 MPa pressure. Some amount of titanium powder was replaced with titanium hydride to obtain the alloy with 0 and 20 at.% hydrogen. After HIP'ing hydrogen was removed by vacuum annealing. Scanning electron microscopy (SEM) was used to study the powder morphologies before and after MA. Phase and microstructural analyses were carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Differential thermal analysis (DTA) was used in conjunction with XRD to determine phase transformations in the compacted materials on heating. Microhardness of the compacts was also determined. The combined MA'ing and HIP'ing process allowed production of a hydrogenated and nanocrystalline γ-TiAl alloy that generally has very low hydrogen solubility.