Microstructure and mechanical properties of Ti–45Al–2W–xC alloys

The microstructure and mechanical properties of five alloys with nominal compositions of Ti–45Al–2W–xC (in at.%), where x is ranging from 0.4 to 2.0 at.%, were studied. The alloys were prepared by vacuum induction melting in graphite crucibles, followed by centrifugal casting into a graphite mould. The as-cast alloys were subjected to hot isostatic pressing and heat treatment consisting of solution annealing, cooling at a constant rate and stabilisation annealing. The microstructure of the heat-treated alloys consists of equiaxed α 2 (Ti 3 Al) + γ(TiAl) lamellar grains surrounded by γ grain boundaries with a small amount of β/B2 particles. The α 2 -α 2 interlamellar spacing λ decreases with increasing carbon content until a solubility limit of carbon is achieved. The increase in carbon content above the solubility limit leads to the formation of primary Ti 2 AlC particles during solidification and an increase in the amount of γ phase at grain boundaries. Vickers microhardness of lamellar grains depends on the carbon content and interlamellar spacing λ. The studied Ti–45Al–2W–0.8C and Ti–45Al–2W–1.2C alloys show improved creep resistance at 800 °C compared to that of the reference carbon-free TiAl–W and carbon-containing TiAl–Nb based alloys with fully lamellar, nearly lamellar, convoluted or pseudo-duplex microstructure. • The microstructure and mechanical properties of five Ti–45Al–2W–xC alloys are studied. • The increase in carbon content leads to a decrease in interlamellar spacing. • Vickers microhardness increases with decreasing interlamellar spacing. • The creep resistance of Ti–45Al–W–0.8C alloy is superior to that of reference alloys. • Carbon stabilises lamellar structure and contributes to precipitation strengthening.