PSI - Issue 42

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Liese Vandewalle et al. / Procedia Structural Integrity 42 (2022) 1428–1435 Vandewalle et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. (a) Full IF spectrum of H-charged cold rolled material (b) H-CW peak of H-charged samples annealed at various temperatures, the fitted relaxation peaks are shown by black lines whereas the cumulative fit is shown in red (c) evolution of the H-CW peak intensity. Evidently, simple tensile deformation is not able to reintroduce the H-CW peak. Therefore, the IF samples are also deformed via torsion of the bar-shaped samples. This torsional deformation differs from the tensile deformation as it results in a much stronger but rather local deformation field. The influence of the induced torsional deformation is shown in Fig. 3. Besides the introduction of strong dislocation relaxation peaks, torsional deformation also results in the reappearance of the H-CW peak. However, it must be noted that the H-CW peak shape is altered, i.e. the relative height of PH2 compared to PH1 has significantly increased. In order to further investigate this reintroduced H-CW peak, the deformed samples are aged at 77°C for various times. The ageing allows better visualization of the H-CW peak as it lowers the background, as can be seen in Fig. 3.b. However, when looking at the evolution of the intensities of PH1 and PH2 visualized in Fig. 3.c, it is clear that even this low temperature annealing results in gradual annihilation of the H-CW peaks. In agreement with the previous measurements, shown in Fig. 1.b and c, PH2 appears to decrease more rapid than PH1. 4. Discussion based on theoretical models In order to understand the H-CW peak behavior, an in-depth analysis is performed based on the two most important existing models describing the CW relaxation, i.e. the Schoeck’s model and the Seeger and Hirth model.

Fig. 2. Influence of tensile straining of recovered material on (a) IF spectrum, (b) TDS spectrum and (c) hardness.