Affiliation: | a Materials Science Division, Bhabha Atomic Research Centre, Trombay, Bombay 400 085, India b IRC in Materials for High Performance Applications, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK |
Abstract: | Gas atomized Ti48Al2Mn2Nb powders were used as a feedstock material for direct laser fabrication (DLF) of near net shape samples. The microstructures of these laser treated samples were characterized using optical, scanning (SEM) and transmission electron microscopy (TEM), both immediately after laser fabrication and after heat treatments. These characterizations have shown that the microstructure is extremely fine but inhomogeneous in comparison to the conventionally processed material. The process parameters such as laser power and scanning speed controlled the microstructural morphology. The laser-treated microstructure remained stable up to 973 K, but rapid grain coarsening occurred at 1273 K. A fully recrystallized, uniform microstructure was obtained after annealing at 1073 K for 24 h, with an apparent compositional homogeneity. Annealing in the phase field followed by air cooling and annealing in (2+γ) phase region resulted in uniform microstructure. However, the microstructure was much coarser than the microstructure of the DLF samples. |