Influence of microstructure refinement on strength, ductility and toughness of TiAl alloys

Trabajo presentado en el MRS Fall Meeting, celebrado en Boston, MA, (Estados Unidos), del 2 al 5 de diciembre de 1996Different Ti-Al alloys with grain sizes ranging from 7μm to 320 nm have been prepared by consolidation of atomised and mechanically milled powders of nominal composition Ti-48Al-2Mn-2Nb and containing carbon additions. The materials obtained consist of equiaxed γ grains containing a distribution of α2 phase mostly along grain or powder boundaries. The high flow strength and low fracture toughness obtained from these materials have been correlated to the fine scale of the microstructure and the transfer of slip across adjacent γ grains. The existence of stress concentrations at boundaries between γ grains leads to emission of curved dislocations and twins. The low mobility of emitted dislocations is responsible for the lack of tensile ductility in these alloys which fail by microcrack formation at grain boundaries.Peer reviewe