X-ray stress measurement by use of synchrotron radiation source

In the field of X-ray stress measurement of polycrystalline materials, a diffraction plane at higher Bragg angle has to be selected in order to obtain the precise value of stress. However, the stress measurement on an optional (hkl) plane desired is not always possible because the X-ray beam exited from a metal target has a dispersive wave length.Recently, we have been able to use the synchrotron radiation source (SR) as an excellent X-ray source. In Japan, the facility of synchrotron radiation (Photon Factory, PF) was constructed in the National Laboratory for High Energy Physics (KEK) at Tsukuba academic city. The use of this SR enables the stress measurements on many (hkl) planes with high accuracy in the higher Bragg angle region by providing an X-ray beam having an optional wave length.We have started the X-ray stress analysis by use of the synchrotron radiation source. This paper reports the system of measurement and some results of preliminaly experiments.Since a monochromatic X-ray beam is required for the stress measurement, we used a beam line which consists of a double crystal monochrometer and a focusing mirror. X-rays between 4KeV (λ=0.31nm) and 10KeV (λ=0.12nm) are available with this optical system. We adopted a constant Bragg angle of 2θ=154° for all the diffraction planes. A PSPC having a carbon fiber anode is made and used as a detector with the use of a fast digital signal processor.We could observe the diffraction profiles from (200), (211), (220), (310) and (321) crystal plane of alpha iron, respectively, and the residual stresses in these planes except the (200) plane were measured with high accuracy in a short time.Such feature especially suits the stress analysis of the material which has preferred orientation or stress gradient.