β 斑对 TB6 钛合金性能及拉伸变形行为的影响

It is generally believed that the “β fleck” in TB6 titanium alloy will reduce the mechanical properties of the component, and the main cause of the β fleck in TB6 alloy is Fe element segregation. In this research, the differences of microstructure, chemical composition and hardness between β fleck and normal area were analyzed by OM, SEM, EDS and EPMA, and the effect of β fleck on the tensile deformation behavior of TB6 alloy was studied. The results show that the content of primary α phase in β fleck is less than 5%, and the β grain size is coarse up to 580 μm, which is more than 60 times of normal grain size. The Vickers hardness of β fleck is slightly higher than that of normal area. The results of composition analysis show that there is no significant difference for V and Fe content between β fleck and normal area, but there are fluctuations and uneven distribution of Fe content within the microregions . Fe content dispersion in β fleck is higher than in normal area. The segregation of V and Fe elements in microregions is the main reason for the difference in the phase transition temperature of TB6 alloy during subsequent heating and deformation. The preconverted β grains grow rapidly due to the lack of pinning by grain boundary α phase. In the process of in situ tension, the crack starts at the grain boundary of the coarse β grain, and grain boundary and intra-crystal slip are the main deformation modes of β fleck structure. The fracture mode of TB6 alloy containing β fleck is intergranular and transgranular mixed fracture mode.