Abstract:The low cycle fatigue (LCF) life and fracture behavior of directionally solidified superalloy DZ4 after torsional pre-deformation and heat treatment was tested and studied. The influence of different pre-deformation extents and rates on LCF life and recrystallization was analyzed. The formation mechanism of intergranular area was investigated. The results show that LCF life of directionally solidified superalloy DZ4 decreases rapidly after torsional pre-deformation and heat treatment, which is related to recrystallization texture in plastically deforming area. Cracks and damages are found on the interface of the recrystallization and the matrix caused by their inharmonious deformation, and the cracks propagate along the recrystallization boundary to form intergranular area, resulting in the decrease of LCF life. Meanwhile the life is decreased sharply with the increase of the recrystallization depth. The depth of intergranular area is in accord with the recrystallization depth when the pre-deformation is small; while when the pre-deformation is larger, the depth of intergranular area is relatively smaller. Besides, the increase of strain rate aggravates inharmonious deformation, and makes recrystallization localize, which cause more serious decrease of LCF.