A. A. Baikov Institute of Metallurgy and Materials Science (Russian Academy of Sciences), Moscow, Russia:

T. K. Akopyan, Post-Graduate Student
A. G. Padalko, Head of Laboratory

V. A. Baklan, Candidate for a Master's Degree

Chair of Casting Processes Technology, National University of Science and Technology “MISiS”, Moscow, Russia:

N. A. Belov, Professor, e-mail: nikolay-belov@yandex.ru
G. C. Zlobin, Candidate for a Master's Degree

Reduction or elimination of casting defects and improvement of mechanical properties (especially, the ductility and fatigue life) are possible due to the hot isostatic pressing of aluminum alloys. For the purpose of obtaining of maximal effect and accelerating of process, the treatment is carried out at high pressures and the temperatures, which are comparable with the quenching heating temperature. In this case, the influence of pressure on the phase-transformation temperatures should be taken into account. The phase transformations in high strength casting nickel-alloyed aluminum alloys were studied for the purpose of determination of the barothermal processing parameters. The characteristic temperatures for the Al – Zn – Mg – (Cu) – Ni – Fe system alloys at atmospheric pressure were obtained by the thermo dynamic calculations and thermal analysis methods (including the differential scanning calorimetry). The phase transition temperatures of three typical alloys (ATs6N4 (АЦ6Н4), ATs7NZh (АЦ7НЖ) and ATs6N0,5Zh (АЦ6Н0,5Ж)) at a pressure of 100 MPa were determined by the previously developed method of differential barothermal analysis. There is found that excessive pressure leads to increasing of characteristic temperature of the alloy by 5–10 degrees (including the solidus). The maximal increasing of the solidus temperature (~10 degrees) was registered for the ATs6N4 and ATs6N0,5Zh alloys. Taking into account the influence of pressure on the solidus, there are proposed the thermal regimes of the hot isostatic pressure of castings. It is recommended to increase the temperature of the hot isostatic pressing, in comparison with the homogenization annealing temperature: increasing of the temperature for the ATs6N4 alloy to 545 ^оC, increasing of the temperature for the ATs6N0,5Zh alloy to 575 ^оC and increasing of the temperature for the ATs7NZh alloy to 535 ^оC.

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