Microstructural Evolution of a Third-Generation Single Crystal Superalloy DD33 During Solution Treatment

Abstract

The microstructural evolution of a third-generation single crystal superalloy DD33 during solution treatment has been investigated by optical microscope(OM),Scanning electron microscope(SEM) and electron probe microanalysis(EPMA).The results show that the g ' particles in interdendritic regions of the alloy grew up obviously during isothermal exposure at 1310℃,and fully dissolved after heat treated at 1310℃/2 h.No significant dissolution of(g +g ') eutectic could be observed when solution treated at temperatures below 1320℃.The cursive-script like MC carbides dissolved gradually and then transform into granular MC particles during solution treatment,which promoted the coarsening of g ' precipitates in the interdendritic regions.The segregation of elements Al,Ta,Cr and Co in the eutectic g ' was enhanced with the increasing temperature,which may be induced by up-hill diffusion.