Refining Ti2AlC particles and improvement of microstructure and mechanical properties on Ti46Al8Nb2.6C alloy by Er addition

Abstract

In order to reveal the refinement mechanism of Er on Ti2AlC particles and lamellae colony, as well as the strengthening mechanism of TiAl composites, Ti–46Al–8Nb-2.6C-xEr as cast alloys were prepared. The microstructure and phase composition were observed by SEM, TEM and X-ray diffraction. Results show that the relative contents of γ phase increase and α phase reduce, the size of lamellae colony decreases from 42.7 to 29.6 μm, lamellae spacing decreases from 0.73 to 0.64 μm and the content of Ti2AlC particles with aspect ratio (1–5) increases from 14 to 47% as Er increases from 0.04 to 0.1 at. %. The orientation relationship with [01‾0]Er2O3// [1‾21‾0]Ti2AlC, (102)Er2O3// (0002)Ti2AlC, (001)Er2O3/// (202‾5)Ti2AlC was observed by TEM. Result shows that Er2O3 particle development on the (0002) of Ti2AlC limits atomic spreading and layered superposition perpendicular to the plane, resulting in Ti2AlC refinement. The compressive strength and the strain increase from 1853 to 2223 MPa and 25.1–25.8% as Er increases from 0.04 to 0.1 at. %. Results of Vickers hardness test displays that Vickers hardness increases from 425.8 to 512.6 HV as Er increases from 0.04 to 0.08 at. %. The significant refinement of Ti2AlC particles by Er2O3 particles, precipitation strengthening of ErAl3 phase, fine grain strengthening of lamellae colony and solid solution strengthening of Er contribute significantly to the better compressive strength.