Research On The First Principle Of Ti₂AlN/TiAl Interface Structures

Ti Al intermetallic alloys have many advantages, such as high specific strength, high specific stiffness, good creep resistance and high temperature strength, it is an ideal material for high temperature structural member. However, low room-temperature ductility and formability limit their applications. The research and development of a variety of Ti Al based composite materials appear, especially the Ti₂Al N/Ti Al composite in recent years. Interface is the key of Ti₂Al N/Ti Al composite quality, but the microscropic study is not enough. We study interface stability, interfacial separation work, the electronic structure of the interface of Ti₂Al N/Ti Al composite using first-principles method.Firstly, we study the structure and stability of Ti Al bulk, Ti₂Al N bulk, seven low index Ti Al surfaces, Ti₂Al N（0001） surface and three terminal Ti₂Al N（112（?）0） surfaces with the the first-principle calculations. For the γ-Ti Al, the energy of Al terminal（110） surface is minimized, and the energy of Ti terminated（001） surface is maximum. For the Ti₂Al N surfaces, the energy of（112（?）0） surface is minimized, the highest is N terminated（0001） surface.Electronic structure analysis of surface effect is mainly caused by the most outer layer and the sencondary layer atoms. The stability of the surface and bonding strength between the atom and the electron structure features are closely related.Secondly, we studied the establishment of five different formed surface of Ti₂Al N/Ti Al composite interfaces. The interfacial separation work of Ti Al（111）/Ntermainated Ti₂Al N（0001） is larger, and interfacial separation work of N in the case of TiAl siting is the largest, it is 5.4676 e V/nm2,the second is N-Ti（N-Al） interface bonding, it is 4.3118 e V/nm2. The interfacial separation work of Ti Al（111）/Ti₂Al N（112（?）0） is also positive, it is 0.25377 e V/nm2. The possibility of the existence of the remaining two interface is lower, because the interface separation work is negative. Interfacial atomic electron density and charge density difference show the combination of N-Ti key strength is the best. Interfacial effect has less influence for the inner atoms, electron transfer occurs mainly near the interface between the atoms.Finally, we observed the interface of Ti₂Al N/Ti Al composite by transmission electron microscope. We observed the existence of the interface of the Ti Al（111）/Ti₂Al N（112（?）0）, and the orientation relationship is [1（?）10]Ti Al//[11（?）00]Ti₂Al N,（111）Ti Al//（11 2（?）0）Ti₂Al N. We also observed the existence of the interface of the（111）Ti Al//（112（?）0）Ti₂Al N, and the orientation relationship is [112（?）0] Ti₂Al N //[1（?）01] Ti Al,（0001） Ti₂Al N //（111） Ti Al. They are the same as the result of simulation. For different observations, it could be the result of a different preparation technology. But both the different results correspond to the simulation.