Thermo-Mechanical Processing and Deformation–Ageing Behavior of a High-Ductile Ni₃Al-Forming Nickel-Based Superalloy

A new Ni₃Al (γ′, L1₂) precipitate-forming nickel-based superalloy composition exhibiting exceptional room-temperature deformability has been developed and processed under controlled laboratory conditions. In contrast to the inherently brittle behavior typically associated with conventional nickel-based superalloys at ambient temperature, the proposed alloy demonstrates remarkable cold-workability, sustaining a rolling height reduction of up to 43% without catastrophic fracture. This enhanced deformability, together with strong resistance to crack initiation and propagation, suggests that the alloy does not follow the conventional deformation response expected of high-strength Ni alloys.

To explore the origins of this unusual behavior, a systematic investigation was carried out across four material conditions: as-cast, rolled, roll-aged, and age-rolled. Mechanical testing, supported by detailed microstructural and fractographic analyses, was employed to identify the characteristic deformation features in each state. The as-cast alloy exhibits a dendritic microstructure, whereas thermo-mechanical processing progressively refines it into a stabilized cellular substructure. Interestingly, hardness measurements show only a weak correlation with cellular or granular feature size, indicating that the strengthening and deformation behavior may be influenced by mechanisms distinct from those commonly observed in Ni-based systems.

The study further compares the influence of ageing treatments—applied before and after deformation—on strengthening behavior and precipitate evolution. The combined changes in microstructure, γ′ morphology, and induced internal stresses appear to play a central role in the alloy’s deformation response and room-temperature workability.

Keywords: Ductile superalloy; Ni₃Al precipitates; Thermo-mechanical processing; Aerospace materials; Deformation mechanisms.