スモールパンチ試験法による鍛造TiAl合金のクリープ特性評価

抄録

In order to investigate the adaptability of small punch (SP) creep testing technique to the local creep property measurement of turbine blade for jet engine, the SP creep test was carried out at the temperatures of 760 and 800°C with a forged Ti-43Al-5V-4Nb alloy. The experimental results showed that the SP creep fracture behavior was macroscopically different between 760°C and 800°C. The ductile creep fracture always occurred at 800°C, while the fracture tended to be brittle at 760°C. However, sometimes the SP specimen was fractured in ductile manner even at 760°C, and this change in fracture mode was closely associated with the large scatter of SP creep rupture time at 760°C. It was revealed by the SP test with a constant deflection rate that the temperature ranges from 760°C to 800°C, in which the SP creep test was performed, corresponded to the ductile-brittle transition temperature of the present alloy. It was also found that there was a good correlation between the load/stress conversion factor (F/σ) and the equivalent fracture strain (ε_ef) measured on the ruptured specimen. Consequently, the SP creep rupture data were relatively well correlated with the uniaxial ones using the above F/σ - ε_ef relationship.