TiAl合金焊接裂纹控制研究进展

The new generation of aerospace engines pursues lightweight and high performance. A large number of new materials and dissimilar materials are selected in the process of engine design and manufacture. TiAl alloy, a high temperature structural material with lightweight and high strength, has gradually entered people's vision. And it has attracted extensive attention in high-tech fields such as aerospace, due to its excellent high-temperature performance and oxidation resistance. It can be predicted that TiAl alloy will become an important engineering material. Thus, it is urgent to investigate the welding technology of TiAl alloy and promote its industrial application. Though, TiAl alloy has prominent high temperature property, it has poor plasticity at room temperature. It is prone to cracks during the welding process, which is particularly severe in fusion welding. As TiAl alloy is a brittle material, the microstructure of the joint is easy to be hardened, during the rapid heating and cooling process. On the other hand, a high thermal stress is accumulated in the joint, causing it to crack. Considering the poor plasticity of TiAl alloy, control of welding crack of TiAl alloy has become the keystone of corresponding research. At pre-sent, the control methods of welding crack mainly include: design of solder composition, alternating nanometric layers, welding with high current, design of metallic interlayers, preheating and post-weld heat treatment, etc. Design of solder composition, alternating nanometric layers and design of metallic interlayers are usually used for non-fusion welding, such as brazing and diffusion bonding. They can decrease the residual stress and reduce the formation of brittle phases. But the mechanical properties of the joint is severely effcted by the intermediate metal. Welding with high current, preheating and post-heat treatment are mostly used for fusion welding of TiAl alloy. The high heat input and long temperature dwell time are benefit for the microstructure transformation of brittle phases and release of high residual stress of the joint. But they can also introduce the coarsen of grains of the joint, which requires further optimization of the welding process. In this paper, the causes of cracking and research progress of crack control are introduced. The application scope and characteristics of diffe-rent crack control methods are analyzed to establish the relationship between microstructure and mechanical properties of the joint. Finally, suggestions for future research about welding of TiAl alloy are proposed.