Assessment of the Al–Fe–Ti system

The Al–Fe–Ti system has been assessed and the limiting binary systems are shortly reviewed. Based on a thorough review of the literature, isotherms at 800, 900, and 1000 °C have been re-evaluated and a provisional isotherm at 1200 °C is presented for the first time. The effect of alloying the binary phases with the third component is reviewed with regard to the ternary homogeneity ranges, crystallography, order/disorder transformations, and site occupancies. Of the variously reported ternary compounds only the existence of “Al2FeTi” (τ2) and “Al8FeTi3” (τ3) is confirmed. The occurrence of the phases τ2*, τ′2, and of a new stacking variant of TiAl is still under discussion, while the existence of the phases Fe2AlTi (τ1) and Fe25Al69Ti6 (X) is ruled out. The presented reaction scheme corroborates the isothermal sections and also a representation of the liquidus surface is given. Magnetic, electrical, thermochemical, atomistic and diffusion data for Al–Fe–Ti alloys are summarised and an overview about studies on modelling of phase equilibria and phase transformations is given

Transformations microstructurales lors de la mécanosynthèse de l'alliage Ti-47.5A1-3Cr

Mechanical milling of pre-alloyed Ti-47.5AI-3Cr (at.%) powder has been carried out in a vibratory mill. The microstructural evolution of the materials was studied as a function of milling time. An ultrafine microstructure was produced with a crystallite size of about 15 nm and a partial amorphization was obtained after 2 hours of milling

MicrostructuralStudies of HIP-Consolidated P/M TiAl+W and TiAl+Cr Powders Subjected to Mechanical Ball Milling

NRC publication: Ye

Decomposition of the β<SUB>o</SUB> phase to the P6<SUB>3</SUB>/mcm, hP18 structure in Nb-(24-36)Ti-40Al alloys

During the course of investigation of the phase equilibria in the Nb-Ti-Al system, decomposition of the ordered B2/β<SUB>o</SUB> phase to an ordered ω-type product was observed in three Nb-(24-36)Ti-40Al (at.%) alloys following aging at 700 °C and on quenching from high-temperatures. Using transmission electron microscopy and X-ray diffraction techniques, this phase was determined as the hP18 variant of the P6<SUB>3</SUB>/mcm structure, with lattice parameters a<SUB>o</SUB> = 7.96 Å and c<SUB>o</SUB> = 5.57 Å, and an α<SUB>o</SUB> ≈ α<SUB>β</SUB>√ 6 and c<SUB>o</SUB> ≈ α<SUB>β</SUB>√ 3 relationship with the parent β<SUB>o</SUB> phase. Ab initio calculations were carried out to estimate the energy of formation of various phases and to also establish the role of Nb in the stabilization of the hP18 phase. The results of the evolution and stability of this structure are presented and discussed