Gradient of Residual Stress and Lattice Parameter in Mechanically Polished Tungsten Measured Using Classical X rays and Synchrotron Radiation

In this work, the stress gradient in mechanically polished tungsten sample was studied using X ray diffraction methods. To determine in depth stress evolution in the very shallow subsurface region up to 10 amp; 956;m , special methods based on reflection geometry were applied. The subsurface stresses depth up to 1 amp; 956;m were measured using the multiple reflection grazing incidence X ray diffraction method with classical characteristic X rays, while the deeper volumes depth up to 10 amp; 956;m were investigated using energy dispersive diffraction with white high energy synchrotron beam. Both complementary methods allowed for determining in depth stress profile and the evolution of stress free lattice parameter. It was confirmed that the crystals of tungsten are elastically isotropic, which simplifies the stress analysis and makes tungsten a suitable material for testing stress measurement methods. Furthermore, it was found that an important compressive stress of about amp; 8722; 1000 MPa was generated on the surface of the mechanically polished sample, and this stress decreases to zero value at the depth of about 9 amp; 956;m. On the other hand, the strain free lattice parameter does not change significantly in the examined subsurface regio