Abstract
The metastable structure of a Ti-48Al-2Cr-2Nb atomised powder is analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), revealing that it mostly contains the α disordered phase, with traces of γ and β/B2 phases. Then, the evolution of the alloy towards its stable (γ+ α₂) structure during continuous heating is studied by differential thermal analysis (DTA), differential scanning calorimetry (DSC) and XRD of heat treated powders. Transformation takes place in a narrow temperature domain, ranging between 620 and 700 °C. It is characterised by a transformation enthalpy of about 2200 J/mol. Uniaxial compression during continuous heating reveals a transient consolidation of the powder in this transformation range, with a relative magnitude of about 1.9 % for a compression stress of 100 MPa. It is proposed that this phenomenon could be due to phase transformation plasticity.

Key words
titanium aluminides, based on TiAl, phase transformation, plastic deformation mechanisms, powder metallurgy, including consolidation, microstructure

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