ANISOTHERMAL HIGH-TEMPERATURE CYCLIC BEHAVIOR OF A Ni-BASED SINGLE CRYSTAL SUPERALLOY
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abstract
Dwell-fatigue tests and variable strain rate tensile tests followed by cycling tests were performed using 001-oriented specimens made of a first-generation Ni-based single crystal superalloy. A short thermal jump from the nominal temperature of 1050C to 1200C was introduced along the lifetime of dwell-fatigue experiments and at the beginning of tensile tests. Once such thermal loading was applied, a fine precipitation occurred in the matrix and induced a large transient strengthening effect on the mechanical properties. Indeed, a transient decrease of the plastic strain rate, corresponding to a reduced magnitude in the hysteresis loops, was measured due to the temperature peak during the dwellfatigue experiments. In addition, a temperature peak produced a large hardening effect during the tensile tests since a hardening of 160 MPa was created. These transient phenomena are due a temporary additional strengthening provided by fine precipitates lasting for the time necessary for their dissolution.