High-density nanoprecipitates and phase reversion via maraging enable ultrastrong yet strain-hardenable medium-entropy alloy

Maraging steels, known for ultrahigh strength and good fracture toughness, derive their superior properties from lath martensite structure with high-density nanoprecipitates. In this work, we designed a novel Fe-based me-dium-entropy alloy with a chemical composition of Fe60Co25Ni10Mo5 in atomic% (at%) by utilizing the char-acteristics of the maraging steels. By a single-step aging of only 10 min at 650 celcius, the alloy showed microstructures consisting of a very high number density of (Fe, Co, Ni)7Mo6-type nanoprecipitates in lath martensite structure and reverted FCC phase, which led to ultrahigh yield strength higher than 2 GPa. Addi-tionally, the alloy exhibited a high ultimate tensile strength of-2.2 GPa and uniform ductility of-6% by harnessing deformation-induced martensitic transformation of the reverted FCC to BCC martensite, which has hardly been exploited in conventional maraging steels. This work demonstrates a novel direction to produce strong and ductile materials by expanding the horizons of material design with the aid of high-entropy concept and overcoming the limits of conventional materials.

Automated summary

In this work, a novel Fe-based medium-entropy alloy was designed based on the characteristics of maraging steels. By a single-step aging at 650 celcius for 10 min, the alloy exhibited microstructures consisting of high-density nanoprecipitates and reverted FCC phase, resulting in ultrahigh yield strength and good ductility.