Anisotropy of high cycle fatigue behavior of a Ni-base single crystal superalloy

摘要

The rotary bending high cycle fatigue properties of a single crystal superalloy in three orientations were tested at 700 °C in ambient atmosphere. The [011] orientation shows the highest fatigue strength. Moreover, the fatigue strength with < 111 > orientation is obviously higher than that with <001> orientation. There are two types of fracture modes, one is cleavage fracture for the [001 ] orientation, the other is the mixed fracture of cleavage and tearing for the [011] orientation. The <011 > orientation shows more pronounced crystal lattice rotation than the < 111 > orientation. Nevertheless, lattice rotation does not occur in the crystals with [001] orientation. Fatigue steps of the [001] and [111] orientated crystals propagate along different {111} glide planes, which means that the slip in <111 > orientation moves more easily than in <011 > orientation. The typical deformation mode of [001 ], [011 ] or [111] orientation is respectively slip bands running through y and y' phases, dislocation pairs shearing y' particles, or superlattice stacking faults besides high-density dislocation shearing y' particles.