PSI - Issue 66

Jinta Arakawa et al. / Procedia Structural Integrity 66 (2024) 38–48 Author name / Structural Integrity Procedia 00 (2025) 000–000

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100μm

(a) IPF map

β phase

100μm

(b) Phase map

Fig. 4. Microstructure of surface of specimen obtained by using EBSD apparatus.

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Applied stress, σ (MPa)

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Strain, ε (%)

Fig. 5. Stress-Strain curve of Ti-22V-4Al.

3.2 Observation and evaluation of the fatigue crack initiation The fatigue crack was identified at 6.2×10 4 cycles, and Fig. 6 shows the direct observation results of fatigue crack growth behavior obtained by OM apparatus. These observations confirm the capability to pinpoint fatigue cracks with high accuracy using direct observation method. Furthermore, fatigue fracture surface is exhibited in Fig. 7. According to this figure, there are no facet in the magnified image of fracture surface around the fatigue crack initiation sites. Therefore. Fatigue crack might be initiated by the slip activation during the cyclic loading. Additionally, the maximum