Effect of grain boundary misorientation on η phase precipitation in Ni-base superalloy 718Plus

Abstract

Abstract In an effort to engineer the morphology of the grain boundaries in Alloy 718Plus to be more damage tolerant, the primary aim of this study was to investigate the effect of the grain boundary misorientation on the precipitation of η phase precipitates. Two types of η phase precipitates were observed to form within the microstructure which formed either lamellar structures or were present as discrete η phase precipitates. The lamellar η phase precipitates were able to induce the formation of serrated grain boundaries, but their precipitation was not correlated to the grain boundary misorientation as they were observed to reside along approximately half of all low angle grain boundaries. However, the average length of the η phase precipitates was found to be affected by the grain boundary misorientation, especially when the precipitates have a low inclination angle with respect to the grain boundary. The presence of discrete η phase precipitates along the grain boundary was found to be a function of the grain boundary as they were preferentially found to form along grain boundaries with high misorientations.