Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8023536 | Surface and Coatings Technology | 2018 | 6 Pages |
Abstract
The residual stresses in a laser shock-peened (LSP) plate of titanium alloy were measured by means of the ring-core Focused Ion Beam-Digital Image Correlation (FIB-DIC) technique using pillar diameters of 10â¯Î¼m and 5â¯Î¼m. A cross-section of the Ti-6Al-4V laser shock peened plate was electrochemically polished to avoid induced residual stress modification due to grinding. FIB-DIC measurements with pillar diameters of 10â¯Î¼m show that a near-surface compressive residual stress of approximately 350â¯MPa is present in the direction parallel to the peened surface. This changes to a tensile residual stress of approximately 100â¯MPa at the depth of 2â¯mm, and then changes back to a small compressive residual stress on the opposite face. These results are in good agreement with the previously obtained set of measurements using high-energy synchrotron X-ray diffraction. However, FIB-DIC measurements with pillar diameters of 5â¯Î¼m show strong deviations from this general macroscopic trend that corresponds to the macroscopic average (Type I) residual stresses. The reason for the apparent discrepancy lies in the smaller gauge volume used in the second set of measurements, which causes the evaluated residual stress values to be dominated by the microscopic (Type IIâ¯+â¯III) residual stress components. These Type IIâ¯+â¯III residual stresses are the result of the local microstructure and intra- and intergranular interactions. The results demonstrate that the FIB-DIC ring-core technique can be tailored to determine either macro- or microscopic residual stress, by tuning the core diameter with respect to the grain size. Type IIâ¯+â¯III stresses have significant magnitude sufficient to produce local tensile stress in the region that is subjected to macroscopic compression due to LSP treatment, and vice versa. The implications of this finding are discussed.
Related Topics
Physical Sciences and Engineering
Materials Science
Nanotechnology
Authors
Joris Everaerts, Xu Song, Balasubramanian Nagarajan, Alexander M. Korsunsky,