from the conferences organized by TANGER Ltd.
Samples of in-situ TiAl-based matrix composite reinforced with Ti2AlC particles were prepared by the centrifugal casting of Ti-47Al-5Nb-1C-0.2B (at.%) alloy. The as-cast samples were subjected to hot isostatic pressing (HIP) at 1360 °C to remove casting porosity. The applied HIP conditions resulted in a significant coarsening of as-cast grain structure connected with deterioration of mechanical properties. Two multi-stage heat treatment routes were proposed to refine the coarse grain structure of the HIP-ed samples. The pre-treatment of the composite in single α phase field followed by air cooling (AC), oil quenching (OQ) or water quenching (WQ) leads to the formation of massive γM(TiAl). The consequent annealing in the γ(TiAl) phase field followed by a stabilisation annealing at 900 °C leads to the formation of homogeneous fine-grained γ type of microstructure in the OQ and WQ samples. The solution annealing of the OQ and WQ samples in the α phase field followed by slow cooling results in the formation of refined equiaxed grains with nearly lamellar α2(Ti3Al) + γ microstructure. The contribution of several mechanisms to the grain refinement is analysed and discussed.
Keywords: TiAl, composites, casting, heat treatments, microstructure© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.