This study investigated the ultra-low-temperature (4.2 K) tensile properties and deformation mechanisms of stainless steel 304L manufactured via laser powder bed fusion (LPBF). The tensile properties of LPBF 304L were compared to those of conventional 304L to assess its suitability for cryogenic applications. The results revealed that LPBF 304L exhibited a significantly higher yield strength but lower ultimate tensile strength and elongation than conventional 304L at 4.2 K. The temperature dependence of the yield strength also favored LPBF 304L. Microstructural analysis demonstrated that LPBF 304L features a high density of dislocation cells and nano-inclusions, contributing to its greater strength. Furthermore, strain-induced martensitic transformation was observed as a key deformation mechanism at cryogenic temperatures, where austenite transformed into both hexagonal-closed packed (HCP) and body-centered cubic (BCC) martensite. Notably, BCC martensite nucleation occurred within a single HCP band. These findings provide critical insights into the mechanical behavior of LPBF 304L at cryogenic temperatures and its potential for applications in extreme environments.

1. Introduction
2. Experimental procedure
    2.1. Materials
    2.2. Ultralow temperature (4.2 K) tensile testing
    2.3. Microstructural observation
3. Results and Discussion
    3.1. Initial microstructure
    3.2. Ultralow temperature (4.2 K) tensile properties
    3.3. Temperature dependence of yield strength for LPBF and conventional 304L
    3.4. Deformation behavior
4. Conclusion
Funding
Conflict of Interest
Data Availability Statement
Author Information and Contribution
Acknowledgments
References

• Seung-Min Jeon(Department of Smart Manufacturing Engineering, Changwon National University, Changwon 51140, Republic of Korea, Korea Institute of Materials Science, Changwon 51508, Republic of Korea)
• Young-Sang Na(Korea Institute of Materials Science, Changwon 51508, Republic of Korea)
• Young-Kyun Kim(Korea Institute of Materials Science, Changwon 51508, Republic of Korea) Corresponding author