Top: Transmission electron images of carbon replicas used to image the γ' precipitates in RR1000 at the start and end of the heat treatment. Bottom: measured particle size distributions and SANS predictions.
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Nickel-based superalloys are a family of materials designed to exhibit both exceptional mechanical properties and superior corrosion resistance at very high temperatures.
Typically, they are the material of choice for the most demanding applications in modern gas turbines. The presence of γ’ Ni3(Al,Ti,Ta) precipitates accounts for their exceptional material performance. The precipitate size and distribution are carefully controlled by heat treatments during manufacturing so as to attain optimal properties.
To investigate γ’ particle size distributions, microscopy is often used, though this technique can only be used before and after heat treatment. An in situ experiment investigating the temporal evolution of γ’ particle size distributions in a RR1000 nickel-based superalloy during aging at 760°C has been performed using small angle neutron scattering (SANS) on LOQ. Due to the high γ’ volume fraction, our data analysis had to account for the scattering from both within and between each distribution. The SANS results will help to validate computer models of precipitates and improve our understanding of these important class of alloys.
DM Collins, HJ Stone (Cambridge University), RK Heenan (ISIS)
Contact: DM Collins, firstname.lastname@example.org
Research date: January 2010
Further information: DM Collins, Met Trans A (accepted, 2010)
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