The UK Realized The Quantitative Prediction Of The Emergence Of High-Cycle Fatigue Cracks In Titanium Alloys
The high-cycle fatigue of titanium alloy parts is one of the main causes of steam turbine failure, and there is an urgent need to better understand the mechanism of crack germination and predict the location of crack germination. The University of Manchester in the United Kingdom used a cyclic four-point bending test to study the relationship between plastic slip activity and fatigue crack formation in near-α-titanium alloy (TIMETABLE ® 834). The results of 2D characterization and 3D-EBSD analysis show that although both along-crystal cracks and through-crystal cracks germinate along the base surface on the surface of the material, the formation process of the crack surface is significantly different. Among them, the crystal crack is related to a special (0001) torsion grain boundary. Compared with the crystal crack, there is almost no plastic deformation at the tip of the crystal crack, which is formed by rapid cleavage and fracture along the (0001) surface, while the crystal crack is formed in multiple steps along the fracture surface near the (0001) surface.
Based on the multi-dimensional understanding of the crack germination mechanism, a brand-new fatigue prediction model is further proposed, and the quantitative prediction of the crack germination location is realized and verified by statistical research. It is of great significance to improve the accuracy of the fatigue life prediction of titanium alloys, and it also provides an important theoretical basis for optimizing the thermal processing process parameters of titanium alloys and extending the service life of engine blades.
