Thermal Expansion of a Multiphase Intermetallic Ti-Al-Nb-Mo Alloy Studied by High-Energy X-ray Diffraction

Intermetallic γ-TiAl-based alloys are lightweight materials for high-temperature applica-tions, e.g., in the aerospace and automotive industries. They can replace much heavier Ni-based alloys at operating temperatures up to 750 ^◦C. Advanced variants of this alloy class enable processing routes that include hot forming. These alloys consist of three relevant crystallographic phases (γ-TiAl, α ₂-Ti ₃Al, β _o-TiAl) that transform into each other at different temperatures. For thermo-mechanical treatments as well as for adjusting alloy properties required under service conditions, the knowledge of the thermal expansion behavior of these phases is important. Therefore, thermal expansion co-efficients were determined for the relevant phases in a Ti-Al-Nb-Mo alloy for temperatures up to 1100 ^◦C using high-energy X-ray diffraction.