Microstructure mechanism, cyclic deformation behavior of an Fe-Ni-Cr alloy considering non-Masing behavior

摘要

The non-Masing behavior of Sanicro 25 alloy was studied during high-temperature low-cycle fatigue (700 degrees C). The results showed that Sanicro 25 alloy exhibits the non-Masing behavior when total strain amplitude (epsilon(a)) increased. The analysis of stable hysteresis loops showed that the stress amplitude (sigma(a)) increased with increasing epsilon(a). At the stable cyclic stage, the rate of increase in sigma(a) with number of cycles increased when epsilon(a) increased. Based on the EBSD observation, the Geometrically Necessary Dislocation (GND) density increased as epsilon(a) increased. The region of high dislocation density was distributed along the grain boundaries, which led to the increasing flow stress. The fraction of twin boundaries decreased and the grain size increased with increasing epsilon(a), which led to a more obvious cyclic yielding stage. Therefore, the non-Masing behavior occurred at a relatively high epsilon(a). Considering the influence of non-Masing behavior on the probability density function relative to the cyclic yield level, the relationship of cyclic stress and plastic strain with the increment of the proportional stress limit delta sigma(0) and Bauschinger strain beta was established. sigma(a) increases linearly with increasing delta sigma(0). sigma(a) decreases with increasing beta.