Development of Fabrication Modes of Deformed Semifinished Products from the Experimental Scandium-Containing Aluminum Alloy and Investigation into Their Mechanical Properties=Разработка режимов получения деформированных полуфабрикатов из экспериментального скандийсодержащего алюминиевого сплава и исследование их механических свойств

Abstract

The urgency of works directed at the fabrication of new alloys of the Al–Mg system alloyed with scandium, which are characterized by a profitable combination of operational and mechanical properties such as weldability, corrosion resistance, and sufficient strength, is shown. Flat ingots of the experimental scandium-containing alloy 560 × 1360 × 4520 mm in size are fabricated in industrial conditions. Modes of thermal treatment and sheet rolling are developed and approved for billets with a maximal thickness of 40 mm cut from them. A DUO 330 mill with flat rolls with an initial diameter of 330 mm and barrel width of 540 mm is used as the rolling equipment. Experimental investigations, which include the preparation of billets to rolling (homogenizing annealing and face milling), hot rolling at 450°C, cold rolling to a thickness of 3 mm, and annealing of cold-deformed semifinished products, result in the fabrication of deformed semifinished products fabricated according to various schemes of reduction during rolling and passed heat treatment. The maximal degree of summary deformation while rolling the billets to a thickness of 3 mm is 92.5%, while drawing for the passage varies from 1.04 to 1.2. Mechanical properties of deformed and annealed semifinished products of various thicknesses made of the experimental alloy are determined using an LFM400 universal test machine with an effort of 400 kN according to GOST (State Standard) 1497–84 and regularities of their variation, depending on the summary degree of deformation during rolling, are revealed. It is established that, when rolling strips made of the experimental scandium-containing aluminum alloy, the temporary tensile strength and yield strength of the material increase, while the relative elongation decreases, which corresponds to general ideas of the theory of metal forming. An analysis of the mechanical properties of the semifinished products shows that the level of strength and plastic properties is rather high, wherein the temporary tensile strength for cold-deformed samples reaches 453–481 MPa, the yield strength of metal reaches 429– 457 MPa, and the relative elongation reaches 3.8–5.0%. The application of annealing made it possible to increase the relative elongation to 14–16% at sufficiently high values of the yield strength (up to 277 MPa). The results of our investigations allow us to develop the modes of casting, rolling, and annealing for the preparation of semifinished products made of the alloy of the Al–Mg system economically alloyed with scandium in limits of 0.10–0.14%, which will be used when approving the machining technologies in industrial conditions.