Development of a Miniaturized Indentation Device for Extremely Low Temperatures Down to 4.2 K

High-precision indentation testing technique has become one of the most widely used tools for investigating the effects of extremely low temperatures on materials and understanding their underlying evolution mechanisms. In this study, a high-precision and miniaturized indentation device (40 mm × 37 mm × 170 mm) for extremely low temperatures down to 4.2 K was developed. The device integrates a novel load-displacement synchronous detection technique that combines dual laser probes with a fixed-ends flexible beam, effectively addressing the challenges of precise measurement of indentation load and displacement under extreme environments. The maximum indentation load of the device is 2 N and the maximum indentation displacement is 20 μm. The stiffness of the flexible beam was calibrated in segments at different temperatures using standard weights, and a nonlinear fitting method was applied to obtain the relationship between machine compliance and temperature. The practicality and reliability of the calibrated device were demonstrated by indentation tests on a fused silica standard sample at room temperature. Indentation tests were carried out on single crystal copper (100) from room temperature of 300 K to extremely low temperature of 4.2 K. Furthermore, mechanical properties and deformation behaviors at extremely low temperatures were also investigated using various characterization techniques. In addition, the self-developed device can be integrated into any commercial physical property measurement system with a sample chamber diameter of more than 49 mm, providing a powerful tool for evaluating material performance in extreme environments.