The development of high γʹ single-crystal Ni-based superalloys for gas turbine applications has focused on creep behaviour in the high-temperature regime above 700 °C. The study of deformation in the range of RT to 700ºC is critical to understanding behaviour in the blade shank of turbine blades in service, as well as the impact of damage during processing at lower temperatures.

In the present work, the commercial alloys CMSX-4®, RR-3010 and TMS-138A* have been systematically studied across a range of temperatures below 650ºC using monotonic tensile testing of nominally [001] oriented specimens. These alloys have been strained to failure at fixed strain rate, and the resulting defect structures characterised using transmission electron microscopy. A number of novel defect structures have been observed. These comprise planar faults, dislocation loops and dipoles and are common to all alloys studied. However these faults change in an alloy-specific manner as a function of temperature, with differing transition temperatures between lower and higher temperature regimes. The novel fault morphologies have been characterised using a variety of techniques. The defect structures will be related to mechanical data from tensile testing.