Microstructural Degradation of Ti-45Al-8Nb Alloy During the Fabrication Process by Electron Beam Melting

The microstructural degradation of the high Nb-TiAl alloy during the fabrication process by electron beam melting (EBM) is reported. The lamellar structure of as-EBM samples in the bottom part of the build shows significant microstructure degradation, resulting in deterioration of tensile properties at both ambient and high temperatures. Microstructural analysis has been conducted by electron backscattered diffraction and transmission Kikuchi diffraction microscopy. The results show that the degradation of the lamellar structure is not only caused by the coarsening under the high-frequency thermal cycling during the fabrication of following layers but also attributed by the discontinuous dynamic recrystallization of the unstable initial lamellar structure resulting from the rapid solidification.