13th International Conference on Fracture June 16–21, 2013, Beijing, China Table 1 LCF test matrix of DZ125 at high temperature 10 1 10 2 10 3 10 4 10 5 400 500 600 700 800 max /MPa Cycles DZ125, 850 o C,R=-1 =1.0% =1.1% =1.2% =1.4% =1.6% (a) 10 1 10 2 10 3 10 4 250 300 350 400 450 500 max /MPa Cycles DZ125,980 o C,R=-1 =0.7% =0.8% =1.2% =1.6% =2.0% (b) Fig. 3 The cyclic stress response curves, (a) 850℃, (b) 980℃ 2.1 Effect of temperature and stress ratio on LCF 10 100 1000 10000 0.5 1.0 1.5 2.0 2.5 3.0 DZ125,R=-1 L,850 o C L,980 o C T,850 o C 45 o ,850 o C Strain range (%) Cycles to Failure (Cycles) Fig. 4 The influence of temperature and load orientation on LCF LCF results at 850 and 980℃ are shown in Fig. 4. Generally, fatigue life at 850℃ is larger than that at 980℃, the fatigue resistance at transverse and 45°orientation is much lower than longitudinal orientation. However, there existing an obvious transition life at short life region, the potential reason may be due to the different cyclic stress response at 850 and 980℃. Although slight cyclic softening phenomenon is happened at 980℃, obvious cyclic hardening phenomenon is happened at 850℃, especially at high strain range (short life region), so maybe the competition between the cyclic hardening induced increased stress and temperature leads to the transition
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