INFLUENCE OF SI CONTENT ON MICROSTRUCTURE OF TIAL ALLOYS

A systematic study of four ternary TiAl-based alloys with constant Ti content of 52.2at.% and variable Si content ranging from 0.3 to 2.7at. % (Al in balance) was conducted. The alloys were prepared from element al powders via a route including powder mixing, precompaction, cold ex trusion, and reactive hot-isostatic pressing. All investigated alloys contain the intermetallic compounds gamma-TiAl, alpha(2)-Ti3Al, and ze ta-Ti-5(Si,Al)(3). The microstructure can be described as a duplex str ucture (i.e., lamella gamma/alpha(2) regions distributed in a gamma ma trix) containing zeta precipitates. With increasing Si content, the nu mber of primary zeta precipitates increased and the gamma grain size b ecame finer while the lamellar volume fraction decreased slightly. (C) Elsevier Science Inc., 1996.