PSI - Issue 13

Kai Suzuki et al. / Procedia Structural Integrity 13 (2018) 1065–1070 Kai Suzuki et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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3. Results and discussion 3.1. Stress-strain and stress amplitude-fatigue life curves

Figure 2 shows the engineering stress-strain curves of the HEA and LEA. Table 2 summarizes the obtained tensile properties. The solid solution-treated HEA had no second phase, but had a similar grain size to that of the LEA. Therefore, the higher 0.2% proof stress of the HEA was attributed to the solid solution strengthening (Abbaschian et al., (2008)). Accordingly, the tensile strength of the HEA was also higher than that of the LEA. Since a higher flow stress easily satisfies the Considère criterion (i.e., d σ t /d ε ε = σ t , where σ t and ε t are the true stress and the true strain, respectively), the elongation of the HEA was lower than that of the LEA.

Fig. 2. Engineering stress-strain curves of the LEA and HEA. Table 2 Tensile test results of the HEA and LEA. Alloy [MPa] . [MPa] [%] HEA 585 254 53 LEA 483 167 81

Figure 3 shows a diagram of the stress amplitude-number of cycles to failure. The fatigue limits of the HEA and LEA were 250 and 200 MPa, respectively. The former was higher than the latter owing to the increase in tensile strength via the solid solution strengthening.

Fig. 3. Relationship between stress amplitude σa and the number of cycles to failure Nf.