Effects of long-term aging at 1070 °C on microstructure of Ni ₃Al-base single-crystal alloy IC6SX

The effects of long-term aging at 1070 °C for periods of 100 h to 1500 h on microstructure of Ni ₃Al-base single-crystal alloy IC6SX were examined by SEM, EDX and TEM. Results show that alloy IC6SX undergoes following microstructure changes during long-term aging: A large number of rod-like Y-NiMo phases and carbides precipitate, and more of them appear in the interdendritic areas than in the dendritic arms; γ-phase aggregate and coarsen, and no longer show a continuous network-like distribution; adjacent y' phases grow bigger and become connected with each other; some larger sized y' phases are discovered in the dendritic arms; after aging for 300 h, γ phases amid a row of adjacent y' phases dissolve to form a y' band, and during further aging, ? phases beside the y' band grow wider and finally occupy the y' band, where a γ band is formed; a small portion of Y-NiMo phases are found to re-dissolve to form gamma; phases after aging for 1500 h.