Effects of Si and C additions on the thermal stability of directionally solidified TiAl–Nb alloys

摘要: Abstract The thermal stability of the lamellar microstructure in TiAl–Nb alloys containing Si and C has been investigated by partial melting experiments. proper compositions, where structure is stable enough to be used as a seed material are found for both TiAl–Nb–Si TiAl–Nb–Si–C alloy systems. Ti–44.5Al–3Nb–0.6Si–0.2C Ti–45Al–2Nb–0.6Si–0.2C (at.%) indeed successfully aligned parallel growth direction directional solidification (DS) with from alloy. DS ingots these exhibit good combination room-temperature ductility (8.5%) high-temperature yield strength (700 MPa at 800 °C). composition range, thermally narrower than corresponding range previously TiAl–Mo–Si TiAl–Si alloys. limits such region discussed terms critical volume fraction α (α 2 ) phase Al-rich side limit α-peritectic Al-lean limit. It concluded that Nb not an effective element improve because upon alloying Nb, no significant change expected occur shift α+γ/γ boundary.