The Changes in Misorientation during the Plastic Deformation of Polycrystalline Metals

Abstract

In a series of studies on the influence of strain history on the plastic deformation of polycrystalline metals, the following experiments were performed in order to make clear the mechanism of plastic deformation of the material subjected to low-cycle tensile pulsating stresses. The measurement of misorientation was made by the use of back-reflection Laue X-ray method, employing the coarse-grained sheet specimens which were constructed with polycrystalline structure and monocrystalline structure respectively. From the viewpoint of crystal plasticity, it will be considered that the aggregate plastic deformation of the polycrystalline metals subjected to low-cycle tensile stressing is mainly interpreted upon the changes in the structure of the material and statistical inhomogeneity of microscopic stress and strain distributions in the material space. From the present experimental examinations, the following conclusions have been derived.(1) The measured values of misorientation in the polycrystalline structural grain under repeated tensile stressing have been found as larger than those in those in the monocrystalline structural grain. Moreover the farmer are dependent on the direction angle of principal strain in the grain.(2) Inhomogeneity in distribution of misorientation is more remarkable in the grains of polycrystalline structure than in those of monocrystalline structure.(3) The difference between the plastic deformation of polycrystalline structural sheet specimen under low-cycle tensile pulsating stresses and that of monocrystalline structural sheet specimen will be interpreted upon the model of mobility of lattice defects which is considered as the changes in structure of the material subjected to the repeated tensile stresses.