Физические методы управления формированием структуры металлов

• Дата: 2023
• Автори: Нурадинов, А. С., Пригунова, А. Г., Шейгам, В. Ю., Вернидуб, А. Г., Нурадинов, И. А.
• Формат: Стаття
• Мова: Українська
• Опубліковано: Physico-technological Institute of Metals and Alloys 2023
• Теми: сплав; кристаллизация; перегрев; переохлаждение; интенсивность охлаждения; вибрация; структура
• Онлайн доступ: https://www.metalsandcasting.com/index.php/mcu/article/view/105
• Назва журналу: Metal and Casting of Ukraine

The aim of this work was to develop scientifically based methods for controlling the formation of a cast structure of metal billets at the first stage of metal production. Using model and metal systems, the possibility of controlling the structure of the workpieces by external physical and thermal effects on the melt during its solidification (overheating, cooling rate, and vibration) was studied. Physical modeling carried out on a flat model of an ingot made of an alloy of camphene with tricyclene made it possible, by regulating the intensity of heat removal during solidification of the melt, to observe in real time the nucleation and growth of crystallization centers, to determine the rate of advancement of the front and the duration of the total solidification time depending on vibration modes. The data obtained on the model alloy on the specifics of the crystallization process due to external physical and thermal influences using the developed method are recalculated for metal objects and verified when studying the formation of the structure of aluminum alloy ingots of technical grade A5 grade. The intensity of heat removal from the hardened metal was controlled by pouring the melt superheated to 750 °C into molds with different wall thickness and thermal conductivity, which ensured a change in the cooling rate from 0.3 °C/s to 5 °C/s. With an increase in the heat sink intensity and vibration exposure to the solidified melt, the kinetics of the crystallization process changes, as a result of which the uniformity and dispersion of the crystal structure of the ingots increase. The results of physical modeling and experiments conducted on metal are in good agreement. The general trend is a significant reduction in the size of macro- and microstructure elements under the influence of vibration. The size of grains and crystals on average decreases by 3–5 times, their size factor decreases in the same ratio, approaching to 1. The microstructure of the ingots is homogeneous, finely crystalline. It has been established that, using a different combination of the considered factors of influence, it is possible to control the processes of crystallization and structure formation. The negative effect of large overheating on the formation of a dispersed dendritic structure can be practically leveled by regulating the intensity of heat removal or by vibrating the liquid and hardening metal.