Strengthening metastable dual-phase Fe60Cr15Ni16Al9 complex concentrated alloy at cryogenic temperature by doping Ti and Mo

The Fe-based complex concentrated alloys (Fe-CCAs) show great potential for advanced structural materials due to their vast alloy compositional spaces, outstanding mechanical properties and low cost of raw material. However, the yield strength of most Fe-CCAs at cryogenic temperature is insufficient, limiting their load-bearing applications under extreme service conditions. In the present work, the additions of Ti and Mo are employed to enhance the tensile properties of metastable dual-phase Fe60Cr15Ni16Al9 CCA. The results show that the yield strength is obviously increased without sacrifice of ductility by substituting the Ti and Mo for Al element. At 77 K, the obtained Fe60Cr15Ni16Al7Ti1Mo1 CCA exhibits superior combination of yield strength and ductility (-1420 MPa and 35%). The increment of yield strength can be explained by the refinement strengthening and solid strengthening induced by doping Ti and Mo. Moreover, adding Ti and Mo will lower the rate of phase transformation and thus retain a relatively stable strain-hardening stage, which finally achieves exceptional ductility. This work provides an effective way to synergistically increase the yield strength and ductility of metastable dual-phase CCAs.