Investigation of the structure and properties of cold-rolled strips from experimental alloy 1580 with a reduced scandium content

Abstract

The structure and properties of cold-rolled strips with a thickness of 3 mm from an experimental aluminum alloy 1580 with a lower scandium content of 0.03% (wt.) relative to the grade of the aluminum alloy and a 5083 similar alloy without scandium were studied. Ingots obtained at the laboratory installation of semicontinuous casting of the foundry department of the Siberian Federal University (Siberian Federal University, Russia, Krasnoyarsk) were used. The preparation of ingots for rolling included milling up to sizes of 40 × 100 × 145 mm and annealing according to a two-stage mode: at a temperature of 350 °C for 3 h (first stage) and at a temperature of 425 °C for 4 h (second stage). Hot rolling was carried out in the laboratory of the Department of Metal Forming at the Siberian Federal University at a temperature of 450 °C on a two-roll hot rolling mill with a roll diameter of 330 mm and a barrel length of 520 mm to a thickness of 5 mm, which corresponded to a total reduction of 88% with a single reduction of 2–5%. For cold rolling, a two-roll sheet rolling mill with a roll diameter of 200 mm and a barrel length of 400 mm grade LS 400 AUTO was used. Rolling was carried out to a thickness of 3 mm with a single reduction of 2–5%, and then the strip was annealed. The results of determining the mechanical properties by tension by the universal LFM400 machine showed that with an increase in the annealing temperature in the range from 250 to 350 °C for 3 h, ultimate tensile strength of the cold-rolled strips of aluminum alloy 1580 decreases from 385 to 365 MPa. For aluminum alloy 5083, a decrease in this strength characteristic is also observed from 345 to 320 MPa. A decreasing tendency with increasing annealing temperature was also observed for the conditional yield strength R_p, and over the entire range of annealing temperatures, the values ​​of R_p for strips of alloy 1580 were higher than for alloy 5083 by 35–40 MPa, which amounted to 14–17% The values ​​of the plastic properties, for which the value of the elongation to failure was analyzed, were close throughout the range of annealing temperatures for both alloys. The results of the analysis of micro- and fine structure allowed to conclude that an increase in the strength properties of cold-rolled and annealed sheets from the experimental alloy 1580, compared with alloy 5083, is a consequence of the addition of scandium in the experimental alloy 1580, which leads to an increase in the temperature of recrystallization of the alloy, preserving it contains a subgrain structure and dispersion hardening caused by precipitation of Al₃(Sc, Zr) phase particles during the decomposition of a solid solution.