Twinning-induced shear fracture of sub-micrometer Ni-based single-crystal superalloys at 900°C

Topologically close-packed (TCP) precipitates and deformation twins significantly impact the high-temperature performances of Ni-based single-crystal (SC) superalloys. However, their contributions to failure of superalloys remain unclear. This study, utilizing in situ thermal-nanomechanical testing at 900°C, reveals a twinning-induced shear fracture in sub-micrometer superalloys containing TCP phases. Under <110>m tension, nanotwins nucleation dominates over the shear sliding at pre-existing σ/matrix interface, inducing shear fracture via the twin boundary (TB) sliding. Density functional theory calculations confirm that TBs exhibit weaker shear resistance than the σ/matrix interfaces. These findings provide insights into twinning-induced premature failure of SC superalloys under service conditions.