Abstract Superalloys exhibit varying deformation mechanisms at differing temperatures and strain rates. The HAYNES ® 244 ® superalloy stands out due to its consistent mechanism of planar fault formation. This distinctive behavior is attributed to the presence of the Ni 2 (Cr, Mo, W) ^{ } γ ″ ′ intermetallic phase, wherein stacking faults form by partial dislocations and subsequently thicken into microtwins via the transmission of partials on adjacent planes. Here we find that, in contrast to conventional ^{ } γ ′ -strengthened superalloys where deformation begins in the γ matrix, twinning in the 244 alloy initiates at the γ – ^{ } γ ″ ′ interface within the ^{ } γ ″ ′ precipitates and then extends outward into the matrix. Our study supports previous hypotheses on twin formation using advanced techniques such as high-resolution scanning transmission electron microscopy, in-situ transmission electron microscopy, and high-strain-rate testing. Contrary to conventional literature, where twinning is often considered detrimental, our work highlights twinning as a unique and significant behavior across temperatures up to the precipitate dissolution temperature and strain rates as high as 500 s −1. In-depth analysis of this alloy at the onset of plasticity and characterization of the γ – ^{ } γ ″ ′ interface highlights a new and additional structural driving force for the stability of the deformation twinning mechanism.
Tucker et al. (2025) studied this question.