Study On The Hydrogenation And The Microstructure And Properties Of Binary Tial Alloy And Ti44Al6Nb1Cr

As the next generation of light and high temperature structural materials, TiAl alloy has excellent properties. In particular, it has the advantages of low density, high specific strength and high specific stiffness. It has great potential for development as engine materials. But TiAl alloy production cost is higher, the application rate is low in the market because of the poor ductility of TiAl alloy at room temperature and high deformation resistance at high temperature. Hot hydrogen treatment technology can reduce the flow stress during hot plastic processing, and improve the deformation limit of cold plastic deformation to optimize the processing properties of the alloy.In this paper, the effects of hydrogen flow rate, hydrogenation time and hydrogenation temperature on the hydrogen content of Ti-44Al-6Nb-1Cr alloy and binary alloy Ti-44 Al and Ti-48 Al were studied. It is found that the hydrogen content increases with the increase of the three factors. Hydrogen flow rate, hydrogenation time have appropriate range, the scope of hydrogenation will be less affected if it is over the range. But when the hydrogen temperature increases, the hydrogen content will increase continuously. Based on this results, the solid state hydrogenation process of binary alloy was optimized.In this paper, the microstructure and mechanical properties of four kinds of TiAl alloys before and after hydrogenation were studied. It is found that the volume fraction of B2 phase in Ti-44Al-6Nb-1Cr alloy is obviously increased, and the intellamellar was thinner. Although the microstructure change of TiAl binary alloy was not obvious, but there was a thin intellamellar thinning phenomenon when the hydrogenation temperature reached the phase transition temperature, The room temperature mechanical properties of TiAl binary alloy were been studied, the room temperature compression testing showed that the room temperature deformation resistance of the two element alloy decreases with the increase of the ultimate deformation rate by the hydrogenation. It means that, the hydrogen can improve the cold plastic forming ability of the binary alloy.The effects of hydrogenation on the high temperature deformation behavior of the four kinds of TiAl alloys were studied by thermal simulation test. Then the mechanism of the subsequent deformation microstructure of hydrogenated alloy during high temperature deformation behavior influence were studied. The results of thermal simulation showed that the flow stress of the alloy decreases obviously when the temperature is increased. However, when hydrogen was used in the same temperature, the influence of the flow stress of the alloy during high temperature deformation was obvious, the flow stress of the alloy decreased with the increase of the hydrogen content in thcenge whole, the peak stress can be reduced by 30-40%. The deformation mechanism of the Ti-44Al-6Nb-1Cr alloy and binary alloy was very different through the research of the deformed microstructure. The deformation of Ti-44Al-6Nb-1Cr depended on the coordination effect of B2 phase. The hydrogen enhanced high temperature plasticity mechanism was mainly causing by the stable element of hydrogen as a β phase to increase the content of B2 phase in the alloy. Then the alloy slip system is increased, deformation coordination performance is enhanced. There is no B2 phase in the binary TiAl alloy, and deformation is mainly depended on the slip and migration of the line defect in γ phase. The deformation resistance of TiAl was large in the early stage of deformation, and the deformation coordination was mainly carried out by dynamic recrystallization in the dynamic softening stage. The further analysis of Ti-44 Al alloy showed that the high temperature increment of hydrogen on the binary alloy is mainly reflected in the promotion of dynamic recrystallization. The hydrogenation of the alloy was favorable to the nucleation and growth of the recrystallization nucleation, which leads to the decrease of the peak stress. Hydrogenation can also promote the dislocation motion. which can achieve high temperature plasticity. The increase of the high temperature plastic of the binary alloy were resulted in the all mentioned factors.