CHARACTERIZATION OF GAMMA' PRECIPITATES IN A SINGLE-CRYSTAL NICKEL-BASE SUPERALLOY SC16 USING SEM, TEM AND SANS AS COMPLIMENTARY MEASURING TOOLS

Characterisation of the microstructure in nickel base superalloys is i mportant for understanding and predicting the behaviour of these compl ex alloys. Large particle sizes of gamma' precipitates in modern alloy s, their regular arrangement in periodic arrays in the gamma matrix an d the complexity of the microstructure evolving under deformation at h igh temperatures, pose serious challenge to the precise characterisati on of the microstructure. This necessitates the use of-complementary m easuring tools e.g. X-ray diffraction, scanning and transmission elect ron microscopy (SEM and TEM), optical metallography etc. Small angle n eutron scattering (SANS) is a useful modern technique, used to charact erise fine precipitates and inhomogenities (<50 nm) in materials. So f ar, established methodology does not exist for using SANS to character ise large particles like gamma' precipitates in superalloys. In this p aper we develop a model to analyse SANS intensity profiles from large (approximate to 400 nm) gamma' precipitates and together with the help of complementary methods such as SEM and TEM, characterise them in a single crystal nickel base alloy SC16.