Tensile Behavior of TMS-238 Ni-Based Single-Crystal Superalloy at 650 °C

TMS-238 is a promising 6th generation superalloySuperalloys with impressive high temperatureHigh temperature creepCreep performance but it exhibits a particular tensile behavior at 650650°C-Tensile behavior °C with low yield strength, limited ductility and a non-classical hardening behavior. To study this behavior, TMS-238 specimens with different misorientationsMisorientation away from the perfect [001] crystallographic orientation were tensile tested at 650 °C. Mechanical tests revealed that highly misoriented specimens do not exhibit this atypical hardening behavior but a classical “plateau” behavior and keep a similar low yield strength. TEM investigations were conducted with post mortem observations in order to interpret these macroscopic tensile characteristics. Similar TEM experiments were also performed using other more classical alloys for reference. TEM investigations in TMS-238Dislocations in TMS-238 revealed a high density of dislocations and stacking faultsStacking faults in the γ phase and a homogeneous deformation in the perfect [001] oriented samples, contrarily to the heterogeneous deformation observed in the misoriented specimen. TEM energy disperse X-ray spectroscopy analysis confirmed significant amounts of Re and Ru in γ, two elements known to increase the γ/γ’ misfitMisfit and decrease fault energy, resulting in a lower mobility of dislocations in the matrix, the presence of extended stacking faultsExtended stacking-fault in the vertical γ-channels and a strong hardening.