LOCAL STRUCTURE AND SOLIDIFICATION OF GLASSFORMING MELT AL₈₆NI₆CO₄GD₂TB₂ UNDER HIGH PRESSURE: EXPERIMENT, MODELING, MACHINE LEARNING

High pressure affects melt solidification and its glass-forming ability. Ab initio molecular dynamics calculations show how the local structure of the melt changes with increasing pressure. High pressure promotes the formation of icosahedral clusters in the melt. Rare earth elements: gadolinium, terbium facilitate the formation of icosahedra. At a pressure of 10 GPa and melt temperature of 1800 K, icosahedra atoms form a "percolation cluster". As pressure decreases, the concentration of icosahedra decreases, and at atmospheric pressure, icosahedra are practically absent. Thus, the glass-forming ability of the melt increases with increasing pressure. Using deep machine learning techniques, the dependence of glass transition temperature on high pressure was evaluated: pressure increase from 0 to 10 GPa increases by 1.3 times. The structure of solid alloy samples obtained by cooling its melt from 1800 K at a rate of 1000 degrees/s under 10 GPa pressure was studied. X-ray diffraction and electron microscopy methods showed that the samples are dense and homogeneous, with a fine-dispersed structure. New crystalline phases with cubic (cP 4 / 2) and tetragonal (tI 26 / 1) structures, stable for long periods under normal conditions, were synthesized in the alloy. Rare earth elements play a major role in the formation of the phase with cubic structur (cP 4 / 2). Studies showed that the average hardness of samples obtained at 10 GPa is almost 2 times higher than that of the initial sample obtained at atmospheric pressure, and is about 2 GPa.