Molybdenum is a strong β-stabilizer and an important alloying element in γ-TiAl based alloys. It offers the opportunity to suppress the formation of α2-phase and is used to generate socalled β/γ-alloys with improved hot working behavior. Unfortunately, the effect of Mo on the individual phases and their transition temperatures during slow heating and rapid cooling in the course of isothermal short and long-term heat treatments is not completely understood. In this paper, the results of investigations of two model alloys with different Mo contents by scanning electron microscopic and calorimetric studies are reported. Below a certain Mo content the high-temperature βphase transforms into α-martensite during water quenching. At higher Mo contents the high-temperature β-phase can be retained upon quenching, only an ordering reaction is observed. Subsequent tempering at 1000℃ leads to a strong grain refinement and hardness reduction.
Titanium aluminides (TiAl) molybdenum (Mo) martensitic trans formation microstructure
Svea Mayer Christian Sailer Thomas Schmoelzer Janny Lindemann Thomas Lipp-mann Masao Takeyama Peter Staron Helmut Clemens
Department of Physical Metallurgy and Materials Testing ,Montanuniversitaet Leoben ,Leoben 8700,Aust Chair of Physical Metallurgy and Materials Technology,Brandenburg University of Technology ,Cottbus Institute of Materials Research ,Helmholtz-Zentrum Geesthacht Outstation at DESY, Hamburg 22607,Germ Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Tokyo 152-8552, Japan Institute of Materials Research, Helmholtz-Zentrum Geesthacht ,Geesthacht 21502 ,Germany