Abstract
The elemental partitioning behavior between gamma and gamma prime phase play an important role for designing a new Ni-based superalloys. The partition behavior of Si would be affected by the strong gamma prime former Ti. EPMA analysis, CALPHAD and first principle simulation are performed to study the effect of Ti on the partition behavior of Si. EPMA result shows that Si would partition to gamma prime phase, while CALPHAD simulation shows that Si have the partition tendency toward gamma phase. Also, both EPMA and CALPHAD simulation shows that Si would partition to gamma matrix more strongly as the content of Ti increase. Based on first principle simulation, Ti atoms would replace Si atoms in gamma prime lattice and reject Si atoms into gamma lattice rather than occupy the Ni-sites in gamma prime lattice. The elemental partition ratio will also change gradually as the aging time increases. Long-term aging and Strain aging process also was conducted to calculate the partition ratio at the system which is closed to the thermodynamic equilibrium state. The existence of point defects would trap Si atom in the gamma prime lattice, so Si would shows the partition tendency toward gamma prime phase in the real experimental cases. The partition behavior of Si between gamma and gamma prime phase is sensitive to the addition of Ti and the system reach the thermodynamic equilibrium or not.