National University of Science and Technology MISIS, (Moscow, Russia)

N. А. Belov, Chief Researcher of the Department of Metal Pressure Treatment, Doctor of Technical Sciences

Siberian Federal University, (Krasnoyarsk, Russia)

V. N. Тimofeev, Professor of the Department of Electrical Engineering of the Polytechnic school, Doctor of Technical Sciences
М. М. Мotkov, Senior Researcher of the Department of Electrical Engineering of the Polytechnic school, Candidate of Technical Sciences

Moscow Polytechnic University, (Moscow, Russia)

S. О. Cherkasov, Associate Professor of the Department of Equipment and Technology of Welding Production, Candidate of Technical Sciences, ch3rkasov@gmail.com

The evolution of the microstructure in an aluminum alloy containing (wt.%): 7.47 Zn, 2.42 Mg, 0.83 Ca, 0.78 Fe, 0.22 Zr, and 0.10 Sc has been investigated during thermomechanical processing from the as-cast state to wire with a diameter of 1.2 mm. The alloy has been produced by electromagnetic casting (EMC) in the form of a 13 mm diameter rod. Extruded rods with a diameter of 3.7 mm have been manufactured from EMC blank homogenized according to the mode of 350 °C for 3h + 450 °C for 3h, using a Conform unit. The extrusion temperature has been 400 °C, and the speed has been 3 rpm. Wire with a diameter of 1.2 mm has been subsequently produced from the extruded rods by intermediate annealing on a medium wiredrawing unit. It has been established that the EMC process, owing to the intensive cooling during solidification (cooling rate exceeding 10³ K/s), promotes the formation of a fine-dispersed microstructure. The dendritic cell size is approximately 5 microns, while all iron in the alloy is contained within submicron eutectic particles of the Al₁₀CaFe₂ phase. During hot Conform extrusion followed by cold drawing, a composite-like microstructure is formed, consisting of globular Fe- and Ca-containing particles (presumably Al10CaFe2 and (Al, Zn)₄Ca) smaller than 500 nm and uniformly distributed throughout the aluminum matrix. Peak hardness (approximately 175 HV) is achieved after aging at 150 °C due to the precipitation of Zn- and Mg-containing secondary phases during strengthening heat treatment. The experimental alloy can be recommended for the fabrication of welded joints by arc welding and laser welding because of the significant fraction of eutectic present in the microstructure.

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