Phase transformation in lamellar system Be/Al/-Fe under isothermal annealing

Full text: The method of plasma sputtering has been used widely for modification of metallic materials. The following thermal treatment needs for adhesion, formation crystal structure and homogenization of formed phases in diffusion zone Initial non equilibrium space distribution of components determine the direction of thermal induced processes of phase transformations. In the present paper the thermal induced processes in lamellar system Be(1.05 μm)-Al(0.95 μm)- Fe(10 μm), obtained by separated deposition of aluminium and beryllium onto α-Fe foils under subsequent thermal annealing, have been investigated. The time of annealing was equals to 50-170 h, the temperatures - 600, 650 and 700 deg. C. We restored the three independent distribution functions: (A) -quadrupole shift ε and two (B and C) - hyperfine magnetic field Hn. The distribution function p(ε) and corresponding to it partial spectrum of paramagnetic type (A) relate to Fe-atoms in aluminides FeAl, Fe2Al5 and FeAl3 or beryllides FeBe5 and FeBex. Distribution function p(Hn) at connecting with it spectrum of magnetic-ordering type (B) relate to intermetallide FeBe2. Distribution function p(Hn) at 210 kG≤Hn≤350 kG, δ≅0 mm/s and corresponding it spectrum (C) was identified to mixed solid solution α-Fe(Al, Be). Dependence of relative intensities I of partial MS-spectra from annealing time tann are shown. Obviously, that relative insensitivities of partial spectrum (A) in high-content aluminides appear in first step of annealing and constitute 2-3 % and practically do not change in 5-40 h, however after tann =60 h they completely disappearance. In this time interval it is observed the increase (from 3 % to 7 %) of relative intensity of partial spectra B, accompanied with decreasing (from 100 % to 90 %) relative intensity partial spectra C. During subsequent annealing up to tann =120 h it is occur a weak change in intensity of partial spectra of magnetic-ordered type (B and C). Then intensity of magnetic-ordered type B tends to zero. In the results of performed studies the sequence of phase transformation and characteristic temperatures of this processes have been established. It was established, that direction of phase transformations has determined by the change of local concentration of components during mutual diffusion process. From Moessbauer data we determined the concentrations of beryllium and aluminum atoms in α-Fe solution during subsequent isothermal annealing