Martensite in a TiAl alloy quenched from beta phase field

• β → α′ martensitic transformation occurred in Ti44Al4Nb4Hf0.1B during quenching.
• Martensite plates have well developed midribs.
• Midribs are the thin layers with high density of stacking faults.
• Habit planes are similar to those in Ti alloys.

Hexagonal martensite with well-developed midribs was obtained by iced-brine quenching of Ti44Al4Nb4Hf0.1Si from the beta phase field. Crystallographic characterisation shows great resemblances of the martensite in this alloy to the lenticular martensite in Fe–Ni alloys in the morphology and substructures of martensite plates. It also bears similarities with the martensite in titanium and its alloys in habit planes and orientation relationship with parent phase. Martensitic transformation under the conditions employed in this work was incomplete and the remaining beta phase after martensitic transformation, thus, underwent diffusional beta-to-alpha transformation or massive transformation, depending on the local circumstances.