  Understanding the creep mechanisms and deformation response at different
stresses and temperatures is crucial for design using nickel-base superalloys
for high-temperature applications. In this study, the creep behaviour of a
newly designed superalloy (nominated Alloy 11) at different stress and
temperature was systematically investigated using SEM, STEM, EBSD and
synchrotron X-ray diffraction. Material properties and mechanical response were
analysed by considering such properties as lattice parameters and misfit, phase
volume fraction, microstrain in reference and crept samples. Detwinning and
dynamic recrystallization were observed for the crept samples. STEM
characterization of deformed materials reveals that multiple deformation
mechanisms and defects could be identified in crept samples, namely,
dislocations in the gamma matrix channels and in gamma prime precipitates,
along with continuous and isolated stacking faults. The highest values of
lattice misfit, microstrain and lattice parameter change were observed at the
centre of dogbone-shaped crept samples. This was associated with the hump
shaped temperature distribution profile during creep testing. The significant
spatial variation detected in terms of lattice parameters, misfit and
microstrain supports the conclusion that it is important to perform spatially
resolved measurements instead of considering each sample as a single
measurement point when investigating creep response. It is also worth noting
that the statistics of the lattice-parameter distribution for the gamma and
gamma prime phases obey a gaussian distribution. In conclusion, a discussion is
given for the meaning and implications of these findings for future research.
