Low cycle fatigue of René 80 as affected by prior exposure

Abstract

Low cycle fatigue of the Ni base alloy Rene 80 was studied at 871°C. Prior to testing, specimens were exposed for 100 h at 982°C either stress-free or at 97 MPa (1/3 the yield). The LCF studies were supplemented by tensile and creep tests. The prior exposure caused significant microstructural changes and life reductions which were most pronounced for stress exposed specimens tested at high rates. Dislocation substructures were extensively studied. The deformation mode was constant for all smooth bar fatigue tests and the dislocation arrangements resembled those seen in creep far more closely than those characteristic of tensile deformation. The observed behavior was attributed to time-dependent changes and environmental interactions. The presence of classical creep/fatigue interactions was considered to be of only minor importance in these experiments.