Deformation mechanisms of FeCoCrNiMo0.2 high entropy alloy at 77 and 15 K.

Deformation mechanisms of high entropy alloys (HEAs) at cryogenic temperatures have attracted extensive research interest. We used in situ neutron diffraction to study the tensile behavior of a face-centered-cubic HEA at 77 and 15 K and compared its stacking fault energy (SFE) at ambient and cryogenic temperatures. The SFE dropped from 28 mJm−2 at 293 K to 11 mJm−2 at 15 K, leading to the transition of deformation mechanism from deformation-induced twinning to martensite phase transformation. As a result, excellent balance of strength and ductility was achieved at both temperatures. This finding highlights the importance of SFE for cryogenic alloy design. Image, graphical abstract [ABSTRACT FROM AUTHOR]