Synchrotron in situ studies of mechanical activation treatment and γ-radiation impact on structural-phase transitions and high-temperature synthesis parameters during the formation of γ-(TiAl) compound.

Abstract

In situ synchrotron studies of structure and phase formation dynamics in mechanically activated (t = 7\u2005min, power density 40\u2005g) and mechanically activated with subsequent irradiation by γ-quanta 60Co powder mixture (Ti\xa064\u2005wt% + Al) during high-temperature synthesis by the method of thermal explosion using induction heating are described. In situ high-temperature synthesis was carried out on the created experimental complex adapted for synchrotron X-ray diffraction methods. The sequence of formation and time-temperature interval of the metastable and main phases were determined. The impact of preliminary mechanical activation and of γ-irradiation on the macrokinetic parameters of the synthesis were studied experimentally in situ. It has been established that the impact of γ-irradiation on the mechanically activated powder mixture of the composition Ti 64\u2005wt% + Al leads to a change in the thermal parameters of combustion: the maximum synthesis temperature and the burning rate decrease. The heating rate for the non-irradiated mixture is 204.8\u2005K\u2005s-1 and that for the irradiated mixture is 81.6\u2005K\u2005s-1. The dependences of mass fractions of the synthesized compounds on time and temperature were calculated from the stage of preheating until completion of the thermal explosion. A single-phase equilibrium product of the composition γ-(TiAl) is formed in γ-irradiated mechanically activated mixture when the system reaches maximum temperature. The synthesized product of the mechanically activated mixture without γ-irradiation contains 72% γ-(TiAl); TiAl3 (26%) and residual Ti (2%) are also observed.