Abstract
In recent years,the Ti2AlNb-based alloys are selected as potential alloys for elevated temperature appli-cations to replace conventional Ni-based superalloys owing to their good creep resistance and oxidation resistance which are related to the O precipitates.In this paper,the precipitation mechanisms of O phase,phase transformation and microstructure control of Ti2AlNb-based alloys are reviewed.Ti2AlNb-based alloys generally consist of B2/β,α2,and O phase with different morphologies which are derived from the various heat treatment processes,including equiaxed α2/O particles,bimodal microstructure,and Wid-mannst(a)tten B2/β + O structures etc.As a newly developed strengthening phase,O precipitates can be precipitated from the B2/β matrix or α2 phase directly as well as generated by means of peritectoid reac-tion ofα2 phase and bcc matrix.Microstructural control of the Ti2AlNb-based alloys can be implemented by refining the original B2/β grain size and regulating the O precipitates.Multidirectional isothermal forging (MIF) and powder metallurgy technique are two effective methods to refine the original B2/β grains and the morphology and size of O precipitates can be regulated by adding alloying components and pre-deformation process.Moreover,the phase diagram as well as coarsening behavior of Ti2AlNb-based alloys in ageing process is also reviewed.For the further application of these alloys,more emphasis should be paid on the deep interpolation of microstructure-property relationship and the adoption of advanced manufacturing technology.
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