Influence of Aging on the Strength and the Elastic Stress Relaxation of the Pre-Deformed MgO Monocrystals

摘要

We identify the differing influence of the aging of the MgO monocrystals that are pre-deformed by uniaxial compression on the acoustic emission (AE) activity and the relaxation processes that are recorded in the microindentation process-which depend on the magnitude of the load P on the indentor: the intensity of the AE after aging increases with the small values of P and, conversely, decreases with the large values. The relaxation coefficient decreases noticeably after aging, but this decrease depends on the degree of the pre-defor-mation. The magnitude of the microhardness of the pre-deformed MgO monocrystals is unstable and changes in the course of the aging process. Its changes in the aging process are determined by the aging time and by the magnitude of the indentor penetration force. It is shown that the auto-emission and relaxation effects that are observed as a result of aging are most likely associated with the presence of the differing layer-by-layer distribution of the elastic stresses in the near-surface layer of the deformed MgO monocrystals. The sign and the magnitude of the stresses change with the depth of the location of the layer and determine the nature of the changes of the subject parameters after aging.