Papers by Author: E.A. Lukina

Abstract: The influence of artificial aging on the phase composition and the properties of sheets made of V-1213 alloy of Al-Cu-Mg-Ag system. It is shown that the phase composition, morphology, dispersion and the density of phase discharge changes with the temperature increase of artificial aging. After the aging at the highest temperature in the range from 150 to 190 °C the maximum density of S' and Ω' phase is observed. This density provides the best combination of mechanical properties when extended at room temperature and high temperature strengthcharacteristics.

Abstract: The fine-fibrous nonrecrystallized structure determines substantial tensile property anisotropy of hot rolled 1424 alloy sheets. In the present work the possibility of producing a fully recrystallized structure in cold rolled sheets was investigated. To improve a technological plasticity a cold rolling was performed after preliminary annealing of hot rolled sheets. The technological plasticity was studied by means of determination a critical deformation degree at plane strain compression at room temperature. The phase composition of hot rolled and annealed sheets was investigated using TEM and X-ray analysis. The uniform fine-grained and fully recrystallized structure in sheets was obtained after rolling with preliminary annealing at 350-380°C and final solid solution treatment. After the indicated above annealing the maximum volume fraction of the equilibrium S1-phase precipitates was observed in the alloy. After cooling in air from the annealing temperature it was found a very small quantity of δ′-phase and after slow cooling with the furnace this phase was practically absent. The fully recrystallized structure in sheets provides a substantial decrease of the tensile property anisotropy in three d irections.

Abstract: The structure of Al-Li-Mg system alloy 1420, containing a small quantity of Sc, Zr, Ti was investigated in cast, homogenized, hot-pressed, quenched and aged conditions, using the methods of optical metallography, transmission electron microscopy and X-ray examination. An existence of areas, having fine grains (20-30 nm)- "Ultrafine Grain areas"(UFGA) was observed in all the investigated conditions. UFGA are located on the boundaries, sub boundaries and S1(Al2MgLi) phase particles. UFGA can also form near the particles of crystallization origin. These areas have a complex phase composition. Inside the UFGA the particles of S1(Al2MgLi) phase and also δnon-phase, investigated in [1] are always present whereas δ'(Al3Li) precipitations are absent. These areas are formed during crystallization and hot deformation. Their composition changes during the treatment. The nature of these changes is considered.

Abstract: The nonequilibrium δnon-phase was originally investigated in the work[1] when studying the ageing processes of the 1424 alloy ( Al-Li-Mg-system). As shown in the work[2] this phase may also be formed during the cooling from the temperature of SSHT. The δnon-phase precipitates are also present in 1420 alloy of the same system[3]. The basic structure investigations were carried out on the 1424 alloy sheets aged in accordance with the regime: 125°C, 32 hrs. The investigations were performed by TEM using the JEOL JEM 200CX microscope. The diffraction patterns from the δnon-phase on the crystallographic axes of zones close to <110>, <111>, <112> were obtained. It can be seen that the regular reflex networks appeared after the deviation from axes of zones by 3-4˚. It was established that the lattice parameters of δnon-phase and its orientation relation with the matrix can be approximately described by the following way: aδnon≈ aα/2[112] b δnon ≈a α/2[110] cδnon≈ a α [111] where aα- the period of the FCC- lattice of solid solution. The model of the crystallographic structure of the δnon-phase precipitates is proposed. On the basis of this model the mechanism of the δnon-phase formation is discussed. The late ageing stages are analyzed and it was shown that the δnon-phase particles are the nuclei for S1(Al2LiMg)- phase.