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 Ni2(Cr, Mo, W) \({\gamma }^{{\prime\prime} {\prime} }\) 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 \({\gamma }^{{\prime} }\) -strengthened superalloys where deformation begins in the γ matrix, twinning in the 244 alloy initiates at the γ– \({\gamma }^{{\prime\prime} {\prime} }\) interface within the \({\gamma }^{{\prime\prime} {\prime} }\) 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– \({\gamma }^{{\prime\prime} {\prime} }\) interface highlights a new and additional structural driving force for the stability of the deformation twinning mechanism.
