Mapping and analysis of microplasticity in tensile-deformed double-notched silicon crystals by computer-aided X-ray double-crystal diffractometry

Abstract

A computer-aided X-ray double-crystal diffractometer was developed to map and analyze rapidly the distribution of plastic and elastic strains in deformed single crystals. It was employed to analyze the microplasticity induced in a double-notched silicon crystal tensile deformed at 800 °C, which was selected as a model material. The study was aimed at exploring the agreement and divergence between micromechanics and macromechanics concepts. The following results were obtained. 1. (1) When long-range interaction effects of the strained plastic zones were negligible by applying small tensile stresses (e.g. 23.4 MPa), plastic zones were formed at the notch tip which were similar to those developed in single-notched specimens. They exhibited shape characteristics in agreement with calculations based on continuum mechanics. 2. (2) With increased deformation the lattice misorientation induced in the internotch region of the specimen increased and was accompanied by modifications of the characteristics of the plastic zone at the notch tips. 3. (3) The microplastic trajectory of the internotch zone, disclosed by the X-ray analysis, outlined the future fracture path of the crystal. 4. (4) The experimentally observed decrease in microplasticity as a function of depth distance from the surface was explained from both the micromechanics and the macromechanics viewpoint. 5. (5) Because of the experimentally observed plasticity gradient from surface to interior, the constraint factor cannot be assumed to be constant.