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

摘要

In situ synchrotron studies of structure and phase formation dynamics in mechanically activated (t = 7min, power density 40g) and mechanically activated with subsequent irradiation by gamma-quanta Co-60 powder mixture (Ti64wt% + 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 gamma-irradiation on the macrokinetic parameters of the synthesis were studied experimentally in situ. It has been established that the impact of gamma-irradiation on the mechanically activated powder mixture of the composition Ti 64wt% + 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 204.8Ks(-1) and that for the irradiated mixture is 81.6Ks(-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 gamma-(TiAl) is formed in gamma-irradiated mechanically activated mixture when the system reaches maximum temperature. The synthesized product of the mechanically activated mixture without gamma-irradiation contains 72% gamma-(TiAl); TiAl3 (26%) and residual Ti (2%) are also observed.