Abstract The results of a study on the strength of rolled products from aluminium alloys doped with scandium under various processing conditions of hot and cold rolling are presented. The regularities of metal flow and the level of strength of deformed semi-finished products from aluminum-scandium alloys are established, depending on the total degree of deformation and the various modes of single reduction during rolling. It is shown that when using one heating of a cast billet to obtain high-quality semi-finished products, the temperature during the rolling process should not be lower than 350-370°, and the total degree of deformation does not exceed 50-60%. It was found that the semi-finished products from alloys with a content of scandium in the range 0.11-0.12% in the deformed state had elevated values of ultimate tensile strength and yield strength of the metal, which allows them to be recommended for industrial production of sheet metal products.

Study of strength properties of semi-finished products from economically alloyed high-strength aluminium-scandium alloys for application in automobile transport and shipbuilding

Results of researches of process of hot rolling of ingots from the experimental aluminum alloy which is economically alloyed by scandium are given. The computer model of process of hot rolling with the use of which the straining, temperature and speed processing modes conditions is calculated and also power parameters of processing is calculated in applied to industrial conditions. It is shown that the use in the model of a certain shape of the ingot faces (Petrov's lock) and indirect rolling action in the edging stand is made it possible to reduce the likelihood of the formation and further development of micro cracks on the edges of rolled metal. The adequacy of results of modeling was confirmed by carrying out pilot-industrial tests when rolling large-size ingots from the experimental alloy and obtaining batches of hot-rolled plates and sheets of various sizes. The tensile test was used to study deformed samples after rolling and samples obtained on five regimes of heat treatment with varying heating temperatures of 300, 350 and 380 oС and holding time in the furnace for 1 and 3 hours. The results of the studies on samples of hot-rolled sheets 10 mm thick showed that, compared with the initial state, the strength characteristics of the metal after heat treatment are reduced by an average of 12-20%, and plastic characteristics increase by 50-65%. In this case, the heat treatment regimes 1 - 3 give a good ratio of the ductility and plastic properties of the metal.

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Modeling and Investigation of the Process of Hot Rolling of Large-Sized Ingots from Aluminum Alloy of the Al-Mg System, Economically Alloyed by Scandium

The structure and mechanical properties of an alloy of the aluminum-magnesium system with a scandium content of no more than 0.1% (wt.) (experimental alloy) at the stages of obtaining sheet semi-finished products have been investigated. The macro and micro structure of cast, hot, and cold rolled sheet semi-finished products has been studied by the methods of light and diffraction transmission electron microscopy, and their mechanical properties have been tested. Casting of ingots, hot, and cold rolling of the alloy was carried out in the conditions of a metallurgical enterprise. The section of the ingots was a rectangle 300 × 1460 mm in size. Preparation of ingots for rolling included milling of all surfaces and two-stage annealing at temperatures of 350 °C (first stage) and 425 °C (second stage). Rolling was carried out across the casting direction. For hot rolling, the billets were heated to 400–410 °C and carried out on a reversible hot rolling mill of grade quart with a roll barrel length of 2800 mm to a thickness of 8.2–9.2 mm. Then, the strips were rolled into rolls and annealed according to the following regime: temperature 390–400 °С, holding for 1 h, cooling with a furnace to 250–270 °С, and unloading into air. Cold rolling was carried out on a QUARTO mill of the CRM grade with a roll barrel length of 2800 mm to a thickness of 5.9–6.3 mm. Microstructural analysis was performed on a Carl Zeiss Axio Observer A1m light microscope using the AxioVision software package. The fine structure of semi-finished products was studied using Tecnai 30 G2 and JEM-2100 EX transmission electron microscopes. The chemical composition of dispersed particles of the secondary phases was determined using energy dispersive X-ray microanalysis (EDX) of thin foils in transmission using an INCA x-sight attachment. It is shown that alloying the experimental alloy with small additions of scandium, zirconium, and manganese leads to the formation of a supersaturated solid solution in the ingot. And upon annealing of the ingot and subsequent hot and cold rolling, a subgrain structure with inclusions of Al6Mn and Al3(Sc, Zr) phases of distribution density is formed in the alloy structure, explaining dispersion and structural hardening of sheet semi-finished products. It was found that the mechanical properties of cold-rolled sheets from the experimental alloy significantly exceed the properties of alloy 5083 with the same magnesium content. But without scandium and are approximately on the same level with alloy 1570 in which the scandium content in comparison with the experimental alloy is three times higher.

Investigation the structure in cast and deformed states of aluminum alloy, economically alloyed with scandium and zirconium

Aluminum alloys doped with scandium represent a new generation of high-performance alloys that have numerous advantages compared to high-strength aluminum alloys. However, the cost of such alloys is quite high. Thus, scientists have been searching for new alloys sparingly doped with Sc that are suitable for industrial use. The current research aims to study the mechanical properties and microstructure of a multi-pass butt-welded joint of plates made of 1580 alloy of the Al-Mg-Zr system sparingly doped with Sc 0.1 wt%, depending on the shape of a weld groove and the chemical composition of the filler wire. Welding of plates with a thickness of 34.5 mm with X-groove and K-groove was performed by the TIG method in manual mode with filler wires from aluminum alloys. Good weldability and hot crack resistance of 1580 alloy providing ultimate strength of welded joints at the level of 0.84–0.93 of the ultimate strength of the base metal were established. The peculiarity of the thermal cycles of multi-pass welding affects the structure formation. The formed coarse-crystalline structure of the weld from 1580 filler wire leads to reduced mechanical properties of the welded joints, compared to the welded joints obtained with the use of 1561 filler wire. The analysis of the macro- and microstructure of the welded joints is given. The results of SEM and EDS studies of welds are presented.

Mechanical properties and microstructure of multi-pass butt weld of plates made of Al-Mg-Zr alloy sparingly doped with scandium

The combination of weldability, corrosion resistance and sufficient strength make it possible to use deformed semi-finished products from the Al-Mg system alloys for sheathing ships' hulls, in car, aircraft and rocket construction, as well as in other areas of industry. To increase the strength characteristics, it is promising to alloy them with small additives of metals such as titanium, zirconium, scandium, and others. In this paper, studies were carried out to obtain deformed semi-finished products (strips, rods and wires) from aluminum alloys in which the scandium content varied from 0.1 to 0.25%. For this purpose, various metal treatment conditions simulated in the laboratory of School of Non-Ferrous Metals and Material Science in Siberian federal university. For the preparation of sheet semi-finished products regimes of hot and cold rolling of a cast billet simulated from a thickness of 40 mm to a thickness of 3 mm. For the preparation of sheet semi-finished products, the modes of hot and cold rolling of the cast billet from a thickness of 40 mm to a thickness of 1-3 mm have been modeled. To produce a welding wire with a size of 2×2 mm, a combined casting and rolling-extruding (CCRE) process was simulated to produce a 9 mm billet and its further rolling in square gauges. Rods with a diameter of 9 mm were produced on a combined processing unit, and wire on a rolling mill with a roll diameter of 130 mm. In accordance with the research program, the mechanical properties of hot-deformed, cold-deformed and annealed sheet semi-finished products were measured. Then the semi-finished products were welded together with the obtained wire and the quality and properties of the welded joint and their corrosion resistance were evaluated. Research results are currently used to develop industrial technologies for the production of sheets and plates from experimental alloys of the Al-Mg system doped with scandium.

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Physical Modeling Technological Regimes of Production Deformed Semi-Finished Products from Experimental Aluminium Alloys Alloyed by Scandium

Siberian federal university, Krasnoyarsk «RUSAL Bratsk Aluminum Smelter» JSC, Bratsk Research results of thermodeformation machining of flat ingots from experimental aluminium alloys, containing magnesium, scandium, rare-earth and transition metals have been represented. Relevance of the work aimed at creating new alloys system Al-Mg, alloyed by scandium, and technologies for obtaining deformed semi-finished products from them using metal forming operations have been shown. Regimes of hot and cold sheet rolling for obtaining strips with thickness 1-3 mm from these alloys were calculated and experimentally tested. Experimental research included the following steps: preparation of flat slabs with dimensions 28×150×300 mm for rolling; hot rolling with temperature 450 C with total draw ratio about 6; cold rolling with total draw ratio about 5; annealing of cold-deformed semi-finished products at temperature 350 C within 3 hours; argon-arc welding of the obtained strips along and across the direction of deformation; Intergranular corrosion test; Evaluation of mechanical properties of the samples. As a result of research nature and degree of corrosion destruction have been studied and Mechanical properties of deformed, annealed and welded semi-finished products from experimental alloys have been determined. It is established that they have a high level of strength and plastic properties of the metal along, across and at an angle 45° relative to the direction of rolling. So tensile strength reaches value 500-520 MPa for deformed samples, yield strength of metal 435470 MPa, relative elongation 4,8-6,7 %, and for annealed samples the values of the relative elongation increase and can reach 14-14,5 % At sufficiently high yield strength 357-369 MPa. Tests for intergranular corrosion of samples after welding showed high corrosion resistance of welded joints, The strength of the welded seam is 0,75-0,85 of the strength of the base metal. The results of research can be recommended for the development of technology for the manufacture of parts from flat products, which including welded joints.

Research of rolling regimes and mechanical properties of cold-rolled, annealed and welded semi-finished products from experimental alloys of Al – Mg system, economically alloyed by scandium

A. I. Bezrukikh

Papers

Research of rolling regimes and mechanical properties of cold-rolled, annealed and welded semi-finished products from experimental alloys of Al – Mg system, economically alloyed by scandium