Problems on the X-Ray Stress Measurement of Polycrystalline Metals (II)

Abstract

In the previous paper, the changes in the lattice strain and the line broadening on the diffraction line were analytically discussed, in view of the elastic anisotropy of crystal, in connection with the mechanism of elastic deformation. It was the aim of the discussion to make clear the relation between the results of the theoretical analysis and the experiments.
Three kinds of materials were used in these experiments, that is, annealed plate specimens of 0.12 percent carbon steel, commercial pure aluminium and copper. All the specimens were electro polished before being exposed to X-rays. The characteristic X-rays of Co Kα, Cr Kα, Fe Kα, and Cu Kα were radiated on the specimen surface through parallel beam slit of divergent angle of 0.25 degree, and the strains were measured by using the diffraction from (422), (420), (400), (331), (310), (220) and (211) atomic planes. The specimens were stressed stepwise by the tensile testing machine, and at several stages of applied stress, the X-ray beams were radiated to the center of the specimen surface in vertical and oblique incidence with several anglesψ. The strain was measured by the conventional sin²ψ method using the counter technique. The value of the lattice strain (ε_ψ) was calculated from the measurement of the diffraction angle of intensity distribution curve by using automatic recorder. From the slope of the lattice strain ε_ψ-σ_m diagram for several applied stresses the ε/σ-sin²ψ curve was drawn by using the method of least square. From these slopes the elastic constant was calculated for each diffraction plane.
The conclusions of the present study are as follows.
(1) The presence of diffraction plane dependence is considered to have been caused by elastic anisotropy. In view of the fact, however, that certain metals contain texture, it is considered to be necessary that the effect of the texture will be taken into consideration in addition to the above mentioned analytical treatment.
(2) In connection with this study, the authors measured the integral breadth in the stage of elastic defomation by the X-ray method, and compared it with the result of analysis of dispersion of micro strain in the stage. The diffraction plane dependence is presented in this case also.