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<p>A series of as-cast Si<sub><i>x</i></sub>Al<sub>0.43</sub>CoCrFeNi<sub>2.1</sub> (<i>x</i> = 0, 0.1, 0.2, and 0.3) high-entropy alloys (HEAs) was successfully fabricated by vacuum-assisted melting. The phase constituents, microstructural features, and mechanical properties (including hardness, tensile behavior, and wear behavior) of alloys with various Si contents were evaluated. The results revealed that the addition of Si promoted the precipitation of a body-centered cubic 1 (BCC1) phase enriched in Al, Ni, and Si with a B2-ordered structure. Furthermore, the secondary BCC2 phase was enriched with Cr, Fe, and Si precipitates within the BCC1 matrix. Ultimately, a multiphase face-centered cubic (FCC)/(BCC1/BCC2) structure was formed. The microstructural evolution driven by Si addition significantly enhanced the mechanical properties of the Si<sub><i>x</i></sub>Al<sub>0.43</sub>CoCrFeNi<sub>2.1</sub> HEAs. As the Si content increased, the microhardness and tensile strength improved by approximately 42% and 55%, reaching 2.359 GPa and 785 MPa, respectively. The quantitative evaluation of the various strengthening mechanisms indicated that the intrinsic hardness of the FCC matrix and hardening due to BCC1/BCC2 precipitation dominated the overall microhardness. The comparison of the energy barriers indicates that BCC2 primarily strengthens the alloy through a shear mechanism rather than an Orowan bypass mechanism. Furthermore, with increasing Si content, reduced friction and wear, together with smoother worn surfaces, reflect a greatly enhanced wear resistance. After the optimal cold-rolling and 1 h annealing at 800°C, the Si<sub>0.3</sub>Al<sub>0.43</sub>CoCrFeNi<sub>2.1</sub> alloy showed 56% and 62% increases in microhardness and tensile strength, respectively, compared to the as-cast state, reaching 3.68 GPa and 1270 MPa. The enhanced mechanical properties are attributed to the synergistic effects of residual strain hardening by FCC ordering and L1<sub>2</sub>/BCC precipitation strengthening.</p>

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Influence of Si addition on the microstructure, mechanical and wear properties of as-cast Al0.43CoCrFeNi2.1 high-entropy alloys and performance enhancement by cold rolling and annealing

  • 期刊论文

  • 发表日期：

    2025年11月24日

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  • Li Wang,
  • Junwei Qin,
  • Yanlin Wang,
  • Xiaohua Chen,
  • Zidong Wang

摘要

A series of as-cast SixAl0.43CoCrFeNi2.1 (x = 0, 0.1, 0.2, and 0.3) high-entropy alloys (HEAs) was successfully fabricated by vacuum-assisted melting. The phase constituents, microstructural features, and mechanical properties (including hardness, tensile behavior, and wear behavior) of alloys with various Si contents were evaluated. The results revealed that the addition of Si promoted the precipitation of a body-centered cubic 1 (BCC1) phase enriched in Al, Ni, and Si with a B2-ordered structure. Furthermore, the secondary BCC2 phase was enriched with Cr, Fe, and Si precipitates within the BCC1 matrix. Ultimately, a multiphase face-centered cubic (FCC)/(BCC1/BCC2) structure was formed. The microstructural evolution driven by Si addition significantly enhanced the mechanical properties of the SixAl0.43CoCrFeNi2.1 HEAs. As the Si content increased, the microhardness and tensile strength improved by approximately 42% and 55%, reaching 2.359 GPa and 785 MPa, respectively. The quantitative evaluation of the various strengthening mechanisms indicated that the intrinsic hardness of the FCC matrix and hardening due to BCC1/BCC2 precipitation dominated the overall microhardness. The comparison of the energy barriers indicates that BCC2 primarily strengthens the alloy through a shear mechanism rather than an Orowan bypass mechanism. Furthermore, with increasing Si content, reduced friction and wear, together with smoother worn surfaces, reflect a greatly enhanced wear resistance. After the optimal cold-rolling and 1 h annealing at 800°C, the Si0.3Al0.43CoCrFeNi2.1 alloy showed 56% and 62% increases in microhardness and tensile strength, respectively, compared to the as-cast state, reaching 3.68 GPa and 1270 MPa. The enhanced mechanical properties are attributed to the synergistic effects of residual strain hardening by FCC ordering and L12/BCC precipitation strengthening.