High temperature deformation of Ti–Al–Nb–Cr–Mo alloy with ultrafine microstructure

• High temperature strength and deformation behavior of TiAlNb-based alloys is studied at various strain rates.
• We examine the effects of introducing the sigma-phase on high temperature performance.
• At lower sigma content, a fine, disconnected microstructure is achievable.
• Deformation and failure mechanisms at elevated temperature are proposed and discussed.

Ti–Al–Nb-based alloys have shown promise for high temperature applications, however limited research has been conducted in γ(TiAl) + σ(Nb2Al) alloys that are aimed towards increasing strength and operating temperatures through microstructural control. Alloys with less than 30% σ-phase have been investigated, exploring relationships between microstructure and deformation mechanisms. An alloy with composition Ti–45Al–14Nb–5Cr–1Mo has been produced, characterized, and tested at high temperature under compression at strain rates ranging from 10−3 to 10−5 s−1. The flow behavior of this alloy shows strain rate and temperature dependence with constant strain rate sensitivity at each temperature in the testing regime. Microstructural analysis reveals the γ-phase is primarily responsible for the alloy's ability to accommodate deformation to large strains under compression.