Effect of deep cryogenic treatment on microstructure and mechanical properties of AlCoCrFeNi2.1 eutectic high-entropy alloy

• Deep cryogenic treatment (DCT) for 36 hours significantly enhances both tensile strength (by 5.74%) and ductility (by 11.79%) of AlCoCrFeNi2.1 eutectic high-entropy alloy, achieving a balanced improvement in mechanical properties. • DCT increases dislocation density in the FCC phase and induces the formation of fine spherical BCC precipitates within the B2 phase, which are key microstructural mechanisms for strengthening. • The study demonstrates that DCT is an environmentally friendly alternative to traditional heat treatment processes, reducing pollution while improving material performance. • The findings provide practical guidance for applying DCT to strengthen 'lamellar + block' type eutectic high-entropy alloys, expanding their potential for advanced structural applications.