Enhanced cryogenic mechanical properties of heterostructured CrCoNi multicomponent alloy: Insights from in-situ neutron diffraction.

Abstract

Heterostructured materials (HSMs) has been shown to improve the strength-ductility trade-off of conventional alloys but their cryogenic performance has not been studied during real-time deformation. We investigated heterostructured CrCoNi medium-entropy alloy by in-situ neutron diffraction at cryogenic (77 K) and room (293 K) temperatures. The significant mechanical mismatch at interfaces between fine and coarse grains, due to pronounced grain size disparity, resulted in exceptional yield strength of 918 MPa at 293 K. The yield strength further increased to 1244 MPa at 77 K with an excellent uniform elongation of 34 %. The exceptional strength–ductility combination at 77 K can be attributed to enhanced geometrically necessary dislocation pile-up density boosted from high-mechanical mismatch interfaces, as well as higher planar faults, and martensitic phase transformation. Comparison with homogenous counterparts demonstrates the potential of HSMs as a new strategy to improve the mechanical performance of different materials, including medium-/high-entropy alloys for cryogenic applications.