Temperature effect on the low cycle fatigue behavior of a directionally solidified nickel-base superalloy

The effect of temperature on low cycle fatigue behavior of a directionally solidified nickel-base superalloy has been investigated from 550 to 850 degrees C. The fatigue life reached maximum at about 700 degrees C. The fracture modes can be divided into three types: crystallographic plane facets fracture (shear fracture) at low temperature region (< 600 degrees C), mixed fracture mode at middle temperature region (600-700 degrees C) and non-crystallographic fracture (I type fracture) at higher temperature region (> 700 degrees C). The dominant reason of the fracture mode transition with temperature is the deformation of the 'gamma' precipitated phase at different temperatures. The precipitated phase is sheared by dislocations which are restricted to the primary {111} slip planes at 600 degrees C. As the temperature increases, the deformation of gamma' precipitated phase becomes anomaly and some secondary precipitates can be observed in the matrix. (C) 2016 Elsevier B.V. All rights reserved.