Cryogenic tensile testing system for simultaneous in situ neutron diffraction and digital image correlation strain analysis.

Abstract

A cryogenic tensile testing system for in situ neutron diffraction measurement, incorporating macroscopic strain distribution measurement through the Digital Image Correlation (DIC) method, was developed. By integrating this system with a versatile horizontal load frame, tensile tests can be conducted within the temperature range from room temperature to 20 K. A tentative measurement combining in situ neutron diffraction and the DIC technique was performed on an ultrafine-grained 304 stainless steel during tensile deformation at 77 K. It revealed that the deformation-induced martensitic transformation can be characterized more accurately by considering the local macroscopic strain in the neutron-irradiated gauge region, as determined by the DIC method, rather than the overall sample strain. The developed system enables accurate measurement of macroscopic strain, particularly in cases of non-uniform deformation, while simultaneously capturing associated crystallographic structure changes, thereby enhancing the effectiveness of neutron data for materials research.