Effect of cylindrical hole configuration and secondary orientation on tensile deformation behavior in Ni-based single crystal superalloys

As a critical material for aero-engine turbine blades, nickel-based single crystal superalloys exhibit deformation behaviors synergistically governed by microstructure, crystallographic orientation, and cylindrical hole configurations. This study systematically investigates the effects of cylindrical hole arrangements (single, triple, and quintuple holes) and secondary orientations (Group A: ; Group B: ) on room-temperature tensile deformation through combined in-situ SEM-EBSD-DIC experiments and crystal plasticity finite element modeling (CPFEM) incorporating dislocation density evolution. Experimental results demonstrated that cooling holes significantly modify local stress states, inducing strain localization and asymmetric slip band distribution around holes. The single-hole specimen (H1-A) developed X-shaped strain concentration zones, while multi-hole configurations (H3, H5) suppressed plastic band propagation through inter-hole stress coupling, thereby enhancing work hardening. Secondary orientation critically influenced deformation mechanisms: Group B specimens (e.g., H3-B) achieved 24% fracture elongation (2.4× higher than Group A's 9.9%) through optimized dominant slip system distribution and coordinated strain accommodation. The CPFEM model successfully replicated experimental strain patterns and slip evolution by implementing dislocation density-based constitutive equations. Combined analysis revealed geometrically necessary dislocations (GNDs) accumulating at deformation band boundaries, with slip systems playing pivotal roles in hardening. Multiaxial stress fields activate slip systems with low Schmid factors, and lattice rotation is correlated with plastic strain gradients and the distribution of GNDs. This work provides cross-scale theoretical guidance for optimizing cooling hole designs and crystallographic orientations in turbine blades, facilitating balanced strength and plasticity.