A Compact Cryogenic Environment for In Situ Neutron Diffraction Under Mechanical Loading

Understanding the deformation mechanisms of materials at cryogenic temperatures is crucial for cryogenic engineering applications. In situ neutron diffraction is a powerful technique for probing such mechanisms under cryogenic conditions. In this study, we present the development of a compact cryogenic environment (CCE) designed to facilitate in situ neutron diffraction experiments under mechanical loading at temperatures as low as 77 K with a maximum cooling rate of 6 K/min. The CCE features a polystyrene foam cryogenic chamber, aluminum blocks serving as neutron-transparent cold sinks, a liquid nitrogen dosing system for cryogen delivery, a nitrogen gas flow control system for thermal management, a process controller for temperature control, and a pair of thermally isolated grip adapters for mechanical testing. The CCE achieves reliable temperature control with minimal neutron attenuation. Utilizing this setup, we conducted three in situ neutron diffraction tensile tests on a 316L stainless steel at 77, 173, and 298 K, respectively. The results highlight the pronounced effects of cryogenic temperatures on the material’s deformation mechanisms, underscoring both the significance of cryogenic deformation studies and the effectiveness of the CCE.