Microstructure evolution behavior of DD6 single crystal superalloy at different using temperatures

The second generation single crystal superalloy DD6 after standard heat treatment was heat-treated at 1100, 1150, 1200, 1250, 1300 and 1320 ℃ for 1 h, respectively, and was then air cooled. The microstructures of the alloy heat-treated at different temperatures were investigated by SEM. The microstructure evolution mechanism of the alloy was estimat using JMatPro software and DSC. The results show that the size of γ′ phase slightly increases after DD6 super alloy heat-treatment at 1100, 1150 and 1200 ℃. The size of γ′ phase increases apparently and its size distribution is very uneven after heat treatment at 1250 ℃. The small part of γ′ phase has serrated γ′/γ phase surface as a result of incomplete solution and the irregular small γ′ phase is major after heat-treatment at 1300 ℃. While the irregular small γ′ phase precipitates again, followed complete solution after heat-treatment at 1320 ℃. The size, shape and volume fraction of γ′ phase vary with the heat treatment temperatures because it grows, dissolves or precipitates again. The volume fraction of γ′ phase decreases to different degrees after heat-treatment at different temperatures except 1100 ℃. There is no fine second γ′ phase in the γ matrix channel of the alloy after standard heat-treatment and heat-treatment at 1320 ℃. But the fine second γ′ phase precipitates in the γ matrix channel after heat-treatment at temperature range of 1100-1300 ℃. Different microstructures are obtained after heat-treatment at different temperatures, which indicates that the using temperature has obvious effect on the microstructure of the alloy. © 2015, Central South University of Technology. All right reserved.