## 3 Results and Discussion
### Hydrogen Embrittlement of 316L Stainless Steel Under Different Hydrogen Storage Conditions
#### 3.2.1 Tensile Properties Under Different Hydrogen Storage Conditions
This enhancement is primarily attributed to martensitic transformation occurring during deformation at cryogenic temperatures due to the material's low stacking fault energy at low temperatures, as previously reported by [PERSON] et al. [21]. Figure 11: Engineering stress–strain curves of 316L stainless steel under different processing conditions at condition 2. Figure 12: Tensile properties of 316L stainless steel under different processing conditions at testing condition 2. The elongation of the as-rolled specimen decreases by 6.5% compared to its performance at room temperature (testing condition 1). However, the effect of cryogenic testing on elongation is less pronounced in additively manufactured specimens than in the as-rolled specimen. This difference is attributed to the non-linear hardening behavior induced by the transformation-induced plasticity (TRIP) phenomenon, as previously reported by [PERSON] et al. (2011). The engineering tensile stress-strain curves and tensile properties of hydrogen-charged specimens tested at cryogenic temperature (testing condition 4) are presented in Figures 15 and 16, respectively. Figure 14: Tensile properties of 316L stainless steel under different processing conditions at testing condition 3. Figure 13: Engineering stress–strain curves of 316L stainless steel under different processing conditions at testing condition 3. As observed, hydrogen charging exhibits a consistent effect on the tensile properties of 316L stainless steel across all material conditions at cryogenic temperature. In all cases, hydrogen-charged specimens demonstrate higher strength and lower elongation compared to specimens tested at cryogenic temperature without hydrogen charging (testing condition 3). These findings align with previously published results [20; 21; 30]. Figure 16: Tensile properties of 316L stainless steel under different processing conditions at testing condition 4. Figure 15: Engineering stress–strain curves of 316L stainless steel under different processing conditions at testing condition 4. Hydrogen Embrittlement Evaluation Using Tensile Properties  
Hydrogen embrittlement refers to the detrimental effect of hydrogen on mechanical properties. The behavior of hydrogen embrittlement in 316L stainless steel is significantly influenced by the manufacturing conditions and the resulting microstructure. As previously mentioned [9; 23; 27], the as-built structure's high dislocation density and cell boundary serve as hydrogen traps, lowering hydrogen diffusivity and postponing the spread of cracks. If properly dispersed, these traps can reduce hydrogen embrittlement, although large stress concentrations can also serve as fracture nucleation sites. High grain boundary areas in the fine microstructure of additively created 316L stainless steel serve as hydrogen traps, particularly at high angles, and carbide precipitation at grain boundaries raises the danger of hydrogen embrittlement. To assess hydrogen embrittlement susceptibility at room temperature, the total elongation at failure of specimens tested in normal air (testing condition 1) was compared with that of hydrogen-charged specimens tested at room temperature (testing condition 2). This comparison quantifies the changes in mechanical properties and evaluates the influence of hydrogen on 316L stainless steel under conditions simulating compressed hydrogen gas storage. To evaluate the hydrogen embrittlement susceptibility of 316L stainless steel under cryogenic conditions, the total elongation at failure of specimens tested at cryogenic temperature (testing condition 3) was compared with that of hydrogen-charged specimens tested at cryogenic temperature (testing condition 4). This comparison simulates the storage conditions of liquid and cryo-compressed hydrogen.