Study On The Migration Behavior Of Oxygen In Ti-Al Based Alloy Under Electromagnetic Suspensio

Ti-Al alloys are now widely used in aerospace engines,automotive structural components,the nuclear industry and in power generation equipment where high temperature stability is required.Due to the limitations of Ti melting and processing,recycling and reuse of Ti scrap is an important way to reduce production costs,but the high content of oxygen in Ti scrap can affect the recycling of Ti alloys.The method of electromagnetic levitation refining can reduce the content of oxygen elements in Ti scrap.In this study,a combination of theoretical calculations and experiments was used to explore the levitation behavior of Ti-Al alloy under electromagnetic levitation conditions and the migration behavior of oxygen elements in the levitation refining process,and the main findings are:（1）The study of the oxygen migration process of Ti-Al alloy under electromagnetic levitation shows that:the key to achieve the levitation and melting of Ti-48Al-2Cr alloy is the magnitude of Lorentz force and Joule heat effect;thermodynamic calculations show that the first element to evaporate under high temperature conditions is Al element followed by Cr element and Ti element;kinetic studies have shown that the migration process of oxygen in the Ti-48Al-2Cr alloy under electromagnetic levitation refining occurs mainly by evaporation in combination with the Al elements in the alloy to form low-valent metal oxides（Al O and Al₂O）.（2）The experimental results of the levitation stability of Ti-48Al-2Cr alloy show that:the number of turns of levitation coil,radius,levitation current and specimen quality affect the levitation stability of Ti-48Al-2Cr alloy,and the best levitation conditions for Ti-48Al-2Cr alloy are obtained through a comprehensive factor levitation stability test:specimen quality of 1.2 g,coil structure of 20mm diameter,number of turns of coil,the levitation current range is 30.2 A-56.2 A.（3）The results of the phase diagram calculation of Ti-48Al-2Cr alloy show that the phases precipitated from Ti-48Al-2Cr alloy in the order of temperature are:liquid phase,αphase,Ti₃Al phase,Laves phase and Ti Al phase;the content of each element in different phases is calculated,the content of Ti Al phase and Laves phase almost does not change with temperature,the content of Ti₃Al phase andαphase increases first and then with the increase of temperature.As the temperature rises,the phase content first increases and then decreases,and when it reaches the melting point the melt will keep the liquid phase state;changing its oxygen element content at different temperatures,it is found that the oxygen element content can affect the changes of the liquid phase and theαphase content,while for the Ti₃Al phase it is affected differently at different temperatures.（4）Different levitation conditions on the migration behaviors of oxygen elements in Ti-48Al-2Cr alloy.The experimental results show that:the migration of oxygen elements in the electromagnetic levitation refining process can be divided into the following processes:oxygen elements are mainly assigned in the form of black particles（Al₂O₃）in the original sample of the alloy;in the levitation refining process,oxygen elements in the molten Ti-48Al-2Cr alloy are mainly in the form of low-valent metal.During the levitation refining process,the oxygen is mainly evaporated from the molten Ti-48Al-2Cr alloy in the form of low-valent metal oxides Al O or Al₂O,while the remaining unevaporated oxygen is mainly existed in the cracks as metal oxides in the levitated Ti-Al alloy.The best levitation temperature and levitation time for oxygen removal was 40 min at 1900℃.