Construction of the nonequilibrium state diagram of the gallium-tin system and its analysis

Thermal analysis methods were used to study the super-cooling of gallium-tin system alloys under normal conditions. For this, the following samples were investigated: Ga (I ); two hypoeutectic alloys 95 % Ga + 5 % Sn (II ), 90 % Ga + 10 % Sn (III ); eutectic alloy 96.3 % Ga + 13.7 % Sn (IV ); five hypereutectic alloy with a Sn content of 20 % (V ), 35 % (VI ), 50 % (VII ), 80 % (VIII ) and pure tin (IX ). The nonequilibrium state diagram of this system was constructed. In this case, the eutectic composition does not change, and the eutectic temperature drops to5.5 °C, i.e. 26 degrees below the temperature of three-phase eutectic equilibrium. The eutectic temperature practically does not change when the eutectic alloy cooling rates vary from 0.06 to 60 °C/min. It was established that a slight decrease in supercooling appears in the hypoeutectic region with an increase in super-cooling observed the hypereutectic region as the alloy composition approaches the eutectic one. The activities and activity coefficients of components on equilibrium and nonequilibrium liquidus lines were calculated. It was shown that the activities of components both on equilibrium and nonequilibrium liquidus lines in general naturally decrease, and the activity coefficients increase as the composition approaches the eutectic one. State diagrams show the concentration paths of equilibrium and non-equilibrium crystallization.

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