Determination of gamma gamma interface types in a gamma TiAl alloy using convergent beam electron diffraction

The orientation relationships between neighboring g laths in a a2 g two phase TiAl alloy containing Mn and Nb as additional alloying elements was analyzed by means of convergent beam electron diffraction. Among the possible interface types, true twin related interfaces were observed most frequently. The frequency of pseudo twin related interfaces is twice as high as the frequency of 120 rotational lamellar interfaces. Antiphase boundaries were rarely observed. The number distribution of g g interfaces is compared with experimental results and theoretical predictions for binary alloys reported in literatur

Characterisation of gamma precipitates in single crystal nickel base superalloy SC16 by small angle neutron scattering

Characterisation of the microstructure in nickel base superalloys is important for understanding and predicting the behaviour of these complex alloys. Large particle sizes of amp; 947; precipitates in modern alloys, their regular arrangement in periodic arrays in the amp; 947; matrix and the complexity of the microstructure evolving under deformation at high temperatures, pose serious challenge to the precise characterisation of the microstructure. This necessitates the use of complementary measuring tools e.g. X ray diffraction, scanning and transmission electron microscopy SEM and TEM , optical metallography etc. Small angle neutron scattering SANS is a useful modern technique, used to characterise fine precipitates and inhomogenities lt; 50 nm in materials. So far, established methodology does not exist for using SANS to characterise large particles like amp; 947; precipitates in superalloys. In this paper we develop a model to analyse SANS intensity profiles from large 400nm amp; 947; precipitates and together with the help of complementary methods such as SEM and TEM, characterise them in a single crystal nickel base alloy SC1