Abstract
Stainless steels are widely recognized for their superior combination of strength, ductility, and corrosion resistance compared to carbon steels, making them attractive candidates for structural and cryogenic applications. Among them, austenitic stainless steels, such as AISI 304, are extensively used in low-temperature environments owing to their excellent toughness and corrosion resistance even under severe sub-zero conditions. In this study, the mechanical behaviour and fracture response of AISI 304 were systematically investigated through cryogenic tensile testing. Cylindrical specimens with a gauge length of 50 mm and diameter of 8 mm were deformed using a Z100 Zwick/Roell universal testing machine equipped with a liquid nitrogen cooling chamber capable of reaching 173 K. Tests were conducted at room temperature (298 K), −30 °C (243 K), −60 °C (213 K), and −80 °C (193 K) under constant strain rates of 10⁻², 10⁻³, and 10⁻⁴ s⁻¹. Temperature stability was ensured by nitrogen gas circulation, while a K-type thermocouple affixed to the specimen surface verified the actual specimen temperature. The results revealed a pronounced strengthening response with decreasing temperature and strain rate. At 10⁻⁴ s⁻¹, the yield strength increased from 611.9 MPa at 298 K to 657.3 MPa at 193 K, while the ultimate tensile strength rose from 810 MPa to 1246 MPa. Similar trends were observed across higher strain rates, confirming the robustness of the strengthening effect. Conversely, elongation decreased gradually, from 0.65 at room temperature to 0.59 at 193 K, indicating reduced ductility. Fractographic analysis demonstrated a transition from ductile dimple rupture at room temperature to mixed-mode fracture with cleavage features at cryogenic temperatures. These findings establish a clear correlation between temperature, strain rate, and fracture mechanisms, providing critical insights into the cryogenic reliability of AISI 304 stainless steel and reinforcing its suitability for advanced applications such as hydrogen storage and low-temperature energy infrastructures.
