Efficient improvement of high-temperature ductility in selective laser melted GH4099 superalloy by Mg microalloying and optimized heat treatment

This work leverages the rapid solidification characteristics of Selective Laser Melting (SLM) technology to mitigate cracking. By alloying minor amounts of Mg as a grain boundary-strengthening element into GH4099 superalloy and employing an improved heat treatment process, mechanisms for improving the high-temperature ductility of the GH4099 superalloy were investigated. The results demonstrate that Mg enriches at the interfaces between grain boundary carbides and the matrix, restricting elemental diffusion between carbides and the matrix, and influencing the morphology and distribution of carbides. Moreover, when Mg added GH4099 superalloy in combination with the improved heat treatment process proposed in this work, the high-temperature ductility efficiently increased from 4.3 % to more than 13.5 %. At this stage, MgO functions as a nucleating site for nanoscale intragranular carbides, leading to a considerable increase in the fraction of Σ3 twin boundaries (12.9 → 88.6 %), while effectively improving ductility at high temperatures.

Duke Scholars

Author Zhaohui Wang Pathology