Research On Reaction Mechanism And Diffusion Reaction Kinetics Of Ti/Al

With the improving need of high temperature structural materials on the properties in the aerospace and automotive field in recent years, the research of Ti-Al alloy brings increasing attention of scholars throughout the world. Ti/Al intermetallic compounds possess many advantages, such as high temperature strength, oxidation resistance, resistance to combustion, low density and so on. Therefore, they become to be the most promising structural materials in the aerospace and automotive field. It is obviously important to research Ti/Al diffusion reaction dynamics and diffusion mechanism so as to provide theoretical basis for manufacturing Ti/Al intermetallic compounds.The intermetallic compounds could be obtained such as TiAl3,Ti3Al,TiAl,TiAl2and Ti2Al5in one kind or more of the following through diffusion reaction between Ti and Al. In different conditions, diffusion reaction kinetics refers to establishing the relationship of product with reaction time and temperature; Diffusion mechanism refers to determining the reaction product and generate order and growth mechanism.The diffusion reaction products and their growth are analyzed in different reaction conditions between Ti and Al by SEM, EDS and XRD.In this paper, Ti/Al diffusion reaction mechanism is studied at low temperature from520to630℃at different time with superfluous Ti and Al materials. Ti/TiAl3diffusion reaction mechanism is studied from630to1150℃at different time. In these conditions, only TiAl3is founded at the Ti/Al interface. Ti and TiAl3are obtianed after getting rid of the surplus Al through diffusion reaction at low temperature. The growth relationship of TiAl3is proposed with various time and temperature. The reaction products of Ti/TiAl3are Ti3Al, TiAl and TiAl2from630to900℃. The reaction products of Ti/TiAl3are Ti3Al, TiAl, TiAl2, and Ti2Al5from1050℃to1150℃.The growth relationship of TiAl3are presented with time and temperature from520to630℃. The growth of TiAl3is parabola law with reaction time. The reaction activation energy of TiAl3is calculated to be170.1kJ/mol and dynamic index n is0.5. TiAl3forms under the action of Ti and Al mutual diffusion, and there are two diffusion mechanisms:lattice diffusion and grain boundary diffusion.The growth relationship of the total layers and the layer of TiAl are presented with time and temperature from630to1150℃. Dynamics equation of the total layers and the layer of TiAl are presented. The reaction activation energy of Ti/TiAl3is79.22kJ/mol and dynamic index n is0.35. The reaction activation energy of TiAl is79.69kJ/mol and dynamic index n is0.5. Ti and Al mutual diffuse in several kinds of intermetallic compounds, and the growth of products in each layer is competitive. Diffusion mechanism includes lattice diffusion and grain boundary diffusion.Ti-Al composite powder pre-blocking is acquired by means of mechanical mixture though different ball mill process, then Ti-Al intermetallic compounds are sintered and manufactured at different temperature and time based on the theory of dynamic equation.