| Abstract Scope |
The application of liquid hydrogen energy in aerospace and deep-sea exploration imposes higher requirements for the reliability of components across a wide temperature range. Medium-entropy alloys (MEAs) are widely concerned because of their excellent mechanical properties. Here, we examined slow strain tensile tests on (VCoNi)96Al2Ti2 MEA and found that the alloy shows greater resistance to HE at 77K than at 298K. Micro-characterizations demonstrate that intergranular fracture dominates at 77K while the transgranular fracture dominates at 298K. Moreover, the transgranular cracks show three paths at both temperatures, which are along the representative {111} slip planes, along the {100} crystal plane and not along any crystal planes. The surprising finding was that the main path of crack growth changes from {111} to {100} with the temperature decrease from 298K to 87K. The difference in temperature dependence of H trapping, dislocation evolution and H-induced cracking was discussed based on the proposed HE mechanism. |