China Advanced Research Reactor (CARR) is a 60 MW tank-in-pool inverse neutron trap type reactor at CIAE. In order to use the non-destructive analytical techniques for phase specific residual stresses research, the new materials science diffractometer RSD was designed at CARR, which is one of the first commissioned instruments to meet the demand of industrial applications. The system comprises two types of monochromator, mosaic flat copper (220) and perfect double focusing silicon (311). The take-off angle of monochromator could change continuously from 41 to 109 degree. Therefore the neutron wavelength varies from 0.895 and 2.666 angstrom. The detector is a one dimension position sensitive detector. Various affiliated equipments enable it to do texture and tensional experiments. The best resolution could reach 0.2% using double focusing Si (311) monochromator. When RSD is available for routine operation, some research work in the field of nuclear industrial and aviatic engineering materials will be carried out using the beam of CARR.

The present work dealt with the fatigue and residual stress (RS) effects of a soft buffer layer (BL) between the parent metal and the weld metal (WM) on welded high-strength low-alloy (HSLA) steel. Six strategies were pursued by varying BL thickness and changing U-notch position with respect to the WM in extended-compact tension specimen. The U-notch position was changed to study the effect of welding RS field, acting along the fatigue crack growth path. The welded HSLAs with BLs strategies were compared to the specimens without BLs strategies, before and after releasing RS respectively. The results demonstrated that the incorporation of a thin BL of 4 mm significantly reduced the fatigue crack growth rate (da/dN) when the RS in the welded HSLA was released by machining a U-notch in the WM. A thick BL of 10 mm was found to be beneficial to fatigue resistance when a U-notch was in the PM.

A mirror furnace for in situ residual stress measurements by neutron diffraction is designed. Bulk and stick sample can be in situ heated up to 1000 degrees centigrade. The stability of the temperature is better than ±1 degree centigrade. This furnace is designed mainly for residual stress neutron diffraction experiments. And also it can be applied to some other neutron instruments such as neutron texture diffractometer, neutron powder diffractometer and triple axis spectrometer.