OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 Considering the ability of 0.5 % hafnium to inhibit discontinuous decomposition, it is worth investigating its eff ect on the microstructure and mechanical properties of the 1570 alloy in the as-cast state and during subsequent thermomechanical treatment. Most 1570 alloy products are thin-walled and are produced from sheets that are supplied in annealed or cold-rolled states, depending on the required properties. Therefore, it makes sense to study the eff ect of 0.5 % hafnium on the microstructure and mechanical properties of the 1570 alloy after these types of treatment. To achieve the study objective, the following tasks need to be addressed: studying nanoparticle formation during 1570 alloy homogenization annealing, as its size and number will dictate alloy structure and properties during subsequent thermomechanical treatment stages. Additionally, the eff ect of 0.5 % hafnium on mechanical properties and grain structure needs to be studied for cold-rolled and annealed states. Study methodology The study focused on the 1570 aluminum alloy and its version with the addition of 0.5 % hafnium. These alloys were chosen based on its chemical composition, which is listed in Table 1. The production of these alloys was carried out in the lab induction furnace UI-25P, and the resulting ingots had dimensions of 20×40×400 mm. Molten metal was cast into a steel chill mold with water cooling at a melt temperature of 720–740 °C. Ta b l e 1 Chemical composition of the studied alloys, % Alloy Al Si Fe Mn Mg Ti Zr Sc Hf 1570 base 0.17 0.26 0.4 6.1 0.03 0.07 0.25 – 1570 0.5Hf base 0.15 0.32 0.42 6.36 0.01 0.04 0.2 0.52 Specimens preparation technology Ingots casting Ingots weighing 5 kg each were produced; with 3 ingots cast per each chemical composition. The charge stock used included A85 grade aluminum, MG90 grade magnesium, and alloying compounds such as Al-Sc2, Al-Zr5, Al-Hf2, and Mn90Al10 tablets. The content of elements was determined according to various standards such as GOST 25086, GOST 7727, GOST 3221, ASTM E 716, and ASTM E 1251 using an atomic emission spectrometer ARL 3460. The required concentration of stock materials, including hafnium, was calculated theoretically since there is a currently no GOST covering hafnium additive. After solidifi cation, the ingots were removed from the mold and water chilled. Homogenization annealing Homogenization annealing at 440 °C for 4 hours dissolves non-equilibrium eutectic and improves chemical homogeneity in aluminum solid solution. Uniaxial tensile tests were conducted on homogenized specimens. Rolling The studied specimens underwent a rolling process. It is important to note that the commercial production of 1570 alloy sheets involves hot rolling above the recrystallization temperature followed by cold rolling. The laboratory rolling process used the same practice in order to produce sheet material. Initially, the specimens were hot rolled in a Duo reversing mill. The process reduced the thickness from 40 mm to 5 mm at a temperature of 440 °С and a roll rotation speed of 3 m/min. After every three passes, the ingots
RkJQdWJsaXNoZXIy MTk0ODM1