The lamellar M

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C

6

phase is a typical harmful microstructure formed in the superalloys including GH4145. The mechanism for the precipitation of the lamellar structure has been investigated extensively

the conditions for the precipitation of the lamellar structure of the M

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C

6

carbide

however

remains unclear till now. By analyzing the precipitation of γ′ and M

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6

phases during the cooling after the 980℃ solution and the subsequent 730℃ aging

it was found that the lamellar M

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6

precipitation was directly governed by t

he γ′ precipitation. After the 980℃ solution

the γ′ precipitation could be prohibited thoroughly when the cooling rate is higher than 22℃/s. During the subsequent 730℃ aging after the 980℃ solution

the M

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6

carbide precipitated as isolated particles when the γ′ phase pre-precipitated in the matrix

because the γ′ phase would inhibit the directional growth of the carbide. While the M

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6

carbide might grow into lamellar form with the γ′ phase by the eutectoid reaction of (M

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6

+γ′) when there was no the γ′ precipitates in the matrix before the aging. The coprecipitation of M

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6

and γ′ is the necessary conditions for the formation of the lamellar M

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6

carbide.