1992 Volume 78 Issue 12 Pages 1854-1861
The nucleation and growth behavior of γ' and η precipitates in A286 was investigated by micro-Vickers hardness test and transmission electron microscopy. The morphology and the crystallography of them were also discussed.
The obtained results are as follows:
(1) The hardness of A286 aged at 893-1073 K for durations up to 720 ks closely related to the mean size of γ' precipitates.
(2)The growth kinetics of the γ' precipitate in η-phase free region was explained by Lifshitz Slyozov-Wagner's theory for diffusion controlled growth at 993-1073K. The activation energy for the growth of the γ' precipitates was estimated to be 283 kJ/mol.
(3) The interlamellar spacing of η-phase in each precipitates was inversely proportional to the degree of undercooling from the equilibrium temperature of γ/(γ+η)-phase boundary.
(4) On the basis of the theory of diffusion controlled eutectoidal growth, the equilibrium temperatures of the cellular and the Widmanstatten precipitation were estimated to be 1218 and 1210K, respectively. These values were consistent with the experimental results.
