Abstract
The present paper describes a surface-microstructural modification due to cold work and the fatigue behaviour of the surface-modified specimens in beta Ti-22V-4Al alloy. As-solution treated specimens were shot peened and then aged to achieve the modification. The obtained microstructure was first characterized and rotating bending fatigue tests were then performed using the surface-modified smooth specimens. The fatigue behaviour was evaluated and compared with the results of the conventional solution treated and aged specimens without modification. Surface-microstructural modification was successfully achieved within the region of 350 μm underneath the surface where hardness increased significantly compared with the core of the specimen, although there were some inhomogeneous precipitation areas in the modified region. The specimens without modification showed a step-wise S-N curve with the transition stress of approximately 600 MPa below which subsurface fracture occurred, while the surface- modified specimens did not exhibit step-wise S-N curve, but both surface-related and subsurface fractures took place up to a higher stress level of 720 MPa, leading to improved fatigue strength. In the surface-modified specimens, several facets were seen at the subsurface crack origin. The initiation sites were deeper than the specimens without modification, which corresponded to the inhomogeneous precipitation areas. The subsurface fracture process is further discussed on the basis of some mechanical approaches.
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Tokaji, K., Takafuji, S., Ohya, K. et al. Fatigue behaviour of beta Ti-22V-4Al alloy subjected to surface-microstructural modification. Journal of Materials Science 38, 1153–1159 (2003). https://doi.org/10.1023/A:1022880914473
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DOI: https://doi.org/10.1023/A:1022880914473