Effects of high-temperature ambient on cyclic fatigue of La_0.8Sr_0.2Mn0_3+8

摘要

The effects of water vapor and oxygen on the cyclic fatigue behavior of oxygen-excess La_0.8Sr_0.2Mn0_3+8 (LSM) were investigated under three-point bending at 1273 K. Because the fatigue life did not obviously depend on the number of cycles, which also represented the effective time of the applied stress, the fracture was presumed to not be significantly controlled by stress-corrosion cracking. Under a low oxygen partial pressure (Po2), however, wet exposure inhibited both fatigue fracture and permanent deformation, in which the LSM crystal lattice was distorted and the unit cell free volume was reduced. Under a high Po2, on the contrary, the crystal symmetry was increased by the wet exposure. The inhibition of fatigue fracture and deformation at both high Ph2o and low Po2 was probably caused by retardation of lanthanum diffusion through its vacancies.