Effect of Aluminum on Microstructure, Mechanical Properties and Castability of a Directionally Solidified Superalloy

Abstract

The effect of aluminum (Al) on microstructure, mechanical properties, solidification behavior, segregation and castability of a directionally solidified Ni-based superalloy was investigated. It was found that the dendrite arm spacing and volume fraction of carbides slightly decreased, while the volume fraction of the γ/γ′ eutectic decreased distinctly with the decrease of Al content. When Al content reduced, the tensile properties at room temperature slightly decreased while the stress rupture life reduced significantly at 980 °C/235 MPa. The change of liquid volume fraction slightly reduced while the residual liquids were more inclined to remain thin continuous network form during the solidification in the alloy with low Al content. The segregation degree of Cr, Mo and W decreased with decreasing Al content, while Co, Al and Ta were more likely to segregate towards the interdendritic regions in the alloy with low Al content. The castability of alloy was getting worse with decreasing Al content.