Materials Science Forum, Vol.455-456, 505-509, 2004
Process development of gamma-TiAl based alloys and their consolidation
The present paper describes part of the work that is being carried out to investigate the formation of Ti-Al-Ag nanostructured intermetallic compounds using Mechanical Alloying (MA). Mixtures of elemental powders with nominal compositions 52TiH(2)-(48-x)AlxAg (x = 0, 2 and 4 at. %) were milled for 25h at 500rpm in a planetary ball mill. The MA led to the formation of a TiH2 (Al) solid solution coexisting with Ll(2)-TiAl3 phase. In all cases, Hot Isostatic Pressing (HIP) at 900degreesC/150MPa/2h and the subsequent heat-treatment at 1200degreesC/4h resulted mainly in gamma-TiAl phase formation. When compared with similar alloys produced in previous work by MA at 200rpm for 50h and consolidated in the same conditions more homogeneous microstructures were obtained. Addition of Ag led to a formation of Ag-rich phases preferential located at the grain boundaries.