Microstructure evolution mechanism of Fe microalloying high Nb–TiAl alloy fabricated by HIP

Ti–45Al–8Nb-0.5 wt%Fe alloy (TiAl–Fe) was ball milled by adding 0.5 wt%Fe to Ti–45Al–8Nb pre-alloyed powder to prepare Fe microalloying high Nb–TiAl alloy by hot isostatic pressing (HIP) process. The microstructure and compressive properties of the TiAl–Fe alloy were systemic studied. The compressive strength of TiAl–Fe samples has been improved to a certain extent. It is found that the content of α 2 phase increases after the addition of Fe element. As hard and brittle phases, B2 and α 2 phases work as obstacles in the deformation, making dislocations accumulate in adjacent γ phase. B2 and α 2 phases indirectly affect the deformation of γ phase by hindering dislocation movement, resulting in stress concentration nearby γ phase. Due to the radius difference between Fe and Al atoms, Fe occupies the position of Al (2e) atoms in γ-TiAl and B2, leading to lattice distortion and dislocation entanglement in γ-TiAl phase. Under the synergistic effect of grain refinement of Fe element and the increase of dislocation density after lattice distortion the strength of the TiAl–Fe is improved.