Effect of aging temperature on the secondary γ′ precipitation in a model Ni based single crystal superalloy

The influence of aging temperature variations ranging from 1120 to 1180 °C on secondary γ′ precipitation in a nickel based single crystal superalloy was investigated. The secondary γ′ precipitates in γ matrix channel were documented only in the sample aging treated at 1180 °C for 4 h, but was not found in the sample aging treated at 1160 °C and below. It was found that the supersaturation of γ′ forming elements in the channel was mainly affected by γ′ fraction. Arise from the decreasing of [Formula presented] by aging temperature falling, the precipitation of secondary γ′ in the channel was blocked and eliminated completely. Though the narrowing of the channel width had helpful to increase the efficiency of atoms migration, which cannot offset the influence of diffusivity decreasing that result from aging temperature reduction. A simple model was proposed in the end to illustrate the different mechanisms of aging temperature and cooling rate.