Grain and lamellar refinement in TiAl based alloy by yttrium addition
(School of Materials Science and Engineering,
Harbin Institute of Technology, Harbin 150001, China)
Harbin Institute of Technology, Harbin 150001, China)
Abstract: The rare earth (RE) element Y was added to binary Ti-48% Al(mole fraction) alloy by induction skull melting. The element Y was added individually 0.5%. The influences of rare earth metal Y on microstructure of as-cast TiAl based alloy was studied by XRD, SEM, EMPA and TEM measurement methodology. The results show that most of rare earth-rich phases (AlY) are uniformly distributed along the grain boundary in the shape of discontinuous network, and some particles of rare earth-rich phases within the grains are mainly ellipsoids. In addition, rare earth element can obviously refine the grain size and the lamellar spacing of as-cast TiAl based alloy samples. The grain size of Ti-47Al-1.2Ce alloy reaches 30-80μm, and the lamellar spacing is less than 200nm.
Key words: TiAl based alloys; thermodynamics; rare earth; microstructure