Temperature-dependent mechanical behavior in a novel hierarchical B2-strengthened high entropy alloy: Microscopic deformation mechanism and yield strength prediction

Abstract

Integration of twinning and hierarchical microstructure into a face-centered cubic (FCC) matrix is a novel research approach for advancing high-temperature alloys, enhancing strength without the need for costly heavy elements. Here, a three-level B2 phase was incorporated into a NiCoCrFe high-entropy alloy (HEA) matrix, offering a high strengthening effect at room temperature and a good resistance to moderate-temperature softening while preserving the low stacking fault energy of the FCC matrix. The resulting NiCoCrFeAl_0.3Si_0.3 HEA exhibited stable yield strength, strain hardening, and deformation twinning over a broad temperature ranging from 77 to 973 K. By establishing a yield strength model based on the various strengthening mechanisms, the study highlighted the important role of the three-level B2 phase in the exceptional mechanical properties of the alloy across a wide temperature range. These findings present a promising avenue for the advancement of high-temperature structural materials.