EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

A detailed study is presented comparing the deformation mechanisms operating at service temperatures in the Ni-based disc alloy RR1000 during monotonic tensile, high stress creep and fatigue conditions. By using bright field conventional and scanning transmission electron microscopy to observe tests interrupted at low strain, it was possible to follow the sequence of events and highlight the many features common to these different deformation modes. While coupled shear of full matrix dislocations forming slip bands is found to different degrees in all test conditions, it is predominantly a process favoured by the high strain rates of tensile and fatigue deformation. The occurrence of stacking fault deformation becomes increasingly prevalent at higher temperature and decreasing strain rate. In this alloy, intragranular carbides appear to act as prolific sources of dislocations which can combine to produce active stacking fault deformation, a feature common to tensile and creep deformation, but there also appears to be the direct emergence of stacking faults from the grain boundaries. While dislocation sources are initially comparable, stacking fault shear plays a negligible role in the analysed fatigue tests. The way in which these detailed observations from monotonic testing can inform the behaviour under complex creep and fatigue conditions is discussed.

Acknowledgements:
This work was supported by Rolls-Royce plc and the EPSRC under EP/H022309/1, EP/H500375/1 and EP/M005607/1.