Temperature and strain-rate effects on low-cycle fatigue behavior of alloy 800H

Abstract

The effects of strain rate (4 × 10^-6 to 4 × 10^-3 s^-1) and temperature on the low-cycle fatigue (LCF) behavior of alloy 800H have been evaluated in the range 750° to 950°. Total axial strain controlled LCF tests were conducted in air at a strain amplitude of ± 0.30 pct. Low-cycle fatigue life decreased with decreasing strain rate and increasing temperature. The cyclic stress response behavior showed a marked variation with temperature and strain rate. The time- and temperature-dependent processes which influence the cyclic stress response and life have been identified and their relative importance assessed. Dynamic strain aging, time-dependent deformation, precipitation of parallel platelets of M₂₃C₆ on grain boundaries and incoherent ledges of twins, and oxidation were found to operate depending on the test conditions. The largest effect on life was shown by oxidation processes.