The creep deformation of a new nickel-base alloy-by-design studied using synchrotron X-ray diffraction

TL;DR

This study investigates the creep behavior of a newly designed nickel-base superalloy using advanced synchrotron X-ray diffraction and microscopy techniques, revealing complex deformation mechanisms and spatial variations in microstructure during high-temperature creep.

Contribution

It provides new insights into the creep mechanisms of Alloy 11, emphasizing the importance of spatially resolved measurements and detailed microstructural analysis for understanding deformation.

Findings

Multiple deformation mechanisms identified, including dislocations and stacking faults.

Significant spatial variation in lattice parameters and microstrain within samples.

Lattice-parameter distribution follows a Gaussian distribution.

Abstract

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.