The inhomogeneity of stress and plastic deformation in neutron-irradiated copper single crystals

Abstract

The plastic deformation in stage I of neutron-irradiated copper single crystals in a uniaxial tensile test is studied at 77 K and room temperature from the view point of stress-inhomogeneity due to the constraint of grips. Primary slip bands appearing in clusters are examined on the two surfaces where the slip step height of a slip band is the maximum by using optical microscopy. Main results are as follows: 1. (i) in the specimen deformed at 77 K, the morphology of primary slip bands and the width of individual clusters of them on one surface are not the same as those on the opposite surface except around the middle part of the specimen; 2. (ii) in the specimen deformed at room temeprature, the difference mentioned in (i) is not found; 3. (iii) in both specimens, the growth of the clusters in width in the upper half of the specimen is larger in the direction of the upper grip than in the direction of the lower grip. This situation is reversed in the lower half. It is concluded that the heterogeneous plastic deformation of neutron-irradiated copper single crystals in a uniaxial tensile test is related with the stress-inhomogeneity caused not only by the constraint of the grips but also by the clustering of primary slip bands.