Enhanced cryogenic mechanical properties of heterostructured CrCoNi multicomponent alloy; Insights from neutron diffraction

Naeem, M.*; Ma, Y.*; Knowles, A. J.*; Gong, W.   ; Harjo, S.   ; Wang, X.-L.*; Romero-Resendiz, L.*; 6 of others*

Heterostructured materials (HSMs) improve the strength-ductility trade-off of alloys, but their cryogenic performance under real-time deformation is unclear. We studied heterostructured CrCoNi medium-entropy alloy via neutron diffraction at 77 K and 293 K. A significant mechanical mismatch between fine and coarse grains led to an exceptional yield strength of 918 MPa at 293 K, increasing to 1244 MPa at 77 K with a uniform elongation of 34%. This strength-ductility synergy at 77 K is attributed to high dislocation pile-up density, increased planar faults, and martensitic transformation. Compared to homogeneous alloys, HSMs show promise for enhancing cryogenic mechanical performance in medium-/high-entropy alloys.