Tailoring Mechanical and Magnetic Properties in Dual-Phase FeCoNi(CuAl)0.8 High-Entropy Alloy
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PROVIDER: S-EPMC10672741 | biostudies-literature | 2023 Nov
REPOSITORIES: biostudies-literature
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Project description:Rational designing of one-dimensional (1D) magnetic alloy to facilitate electromagnetic (EM) wave attenuation capability in low-frequency (2-6 GHz) microwave absorption field is highly desired but remains a significant challenge. In this study, a composite EM wave absorber made of a FeCoNi medium-entropy alloy embedded in a 1D carbon matrix framework is rationally designed through an improved electrospinning method. The 1D-shaped FeCoNi alloy embedded composite demonstrates the high-density and continuous magnetic network using off-axis electronic holography technique, indicating the excellent magnetic loss ability under an external EM field. Then, the in-depth analysis shows that many factors, including 1D anisotropy and intrinsic physical features of the magnetic medium-entropy alloy, primarily contribute to the enhanced EM wave absorption performance. Therefore, the fabricated EM wave absorber shows an increasing effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm. Thus, this study opens up a new method for the design and preparation of high-performance 1D magnetic EM absorbers.
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Project description:Paracrystalline state achieved in the diamond system guides a direction to explore the missing link between amorphous and crystalline states. However, such a state is still challenging to reach in alloy systems in a controlled manner. Here, based on the vast composition space and the complex atomic interactions in the high-entropy alloys (HEAs), we present an "atomic-level tailoring" strategy to create the paracrystalline HEA. The addition of atomic-level Pt with the large and negative mixing enthalpy induces the local atomic reshuffling around Pt atoms for the well-targeted local amorphization, which separates severe-distorted crystalline Zr-Nb-Hf-Ta-Mo HEA into the high-density crystalline MRO motifs on atomic-level. The paracrystalline HEA exhibits high hardness (16.6 GPa) and high yield strength (8.37 GPa) and deforms by nanoscale shear-banding and nanocrystallization modes. Such an enthalpy-guided strategy in HEAs can provide the atomic-level tailoring ability to purposefully regulate structural characteristics and desirable properties.
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Project description:A prototypical, single-phase, and non-equiatomic high entropy alloy Fe40Mn40Co10Cr10 has been mechanically deformed at room and cryogenic temperatures. Plastic deformation was accommodated via crystallographic slip at room temperature while transformation induced plasticity (TRIP) has been observed in samples deformed at 77 K. The stress-induced martensitic transformation occurred from face-centered cubic (FCC) to hexagonal close-packed (HCP) structures. A detailed electron backscatter diffraction analysis was utilized to detect phase change and evaluate the evolution of the HCP phase volume fraction as a function of plastic strain. Physical properties of undeformed and deformed samples were measured to elucidate the effect of deformation-induced phase transitions on the magnetic and electrical properties of Fe40Mn40Co10Cr10 alloy. Relatively small magnetic moments along with non-saturating magnetic field dependencies suggest that the ground state in the considered material is ferrimagnetic ordering with coexisting antiferromagnetic phase. The temperature evolution of the coercive fields has been revealed for all samples. The magnitudes of the coercive fields place the considered system into the semi-hard magnetic alloys category. The temperature dependence of the zero-field cooled (ZFC) and field cooled (FC) magnetization was measured for all samples in the low field regime and the origin of irreversibility in ZFC/FC curves was discussed. Besides, the temperature dependence of the resistivity in all samples was measured and the possible conduction mechanisms were discussed.
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Project description:The microstructure, temperature-dependent mechanical properties and deformation behaviors of equiatomic CoCrFeMnNi high-entropy alloy (HEA) additively manufactured by selective laser melting (SLM) were investigated. SLM-built HEA had a face-centered cubic (FCC) single-phase random solid solution. In addition, SLM-built HEA was composed of epitaxial growth grains, dislocation network and nano-sized oxides. Room- and high-temperature compression tests confirmed that SLM-built HEA has outstanding mechanical properties in all temperature ranges compared to equiatomic CoCrFeMnNi HEAs reported up to the present. The excellent mechanical properties of SLM-built HEA were achieved with fine grains, high dislocation density and fine precipitates at low temperatures (25 °C to 600 °C), and by high dislocation density and fine precipitates at high temperatures (700 °C or higher). On the other hand, the deformation microstructure showed that slip and deformation twins are the main deformation mechanisms from 25 °C to 600 °C, and slip and partial recrystallization are the main deformation mechanisms above 700 °C. Based on the above findings, this study also discusses correlations among the microstructure, superior mechanical properties and deformation mechanisms of SLM-built equiatomic CoCrFeMnNi HEA.
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Project description:This work systematically investigated the relationship between the microstructure, and mechanical and magnetic properties of FeCoNiAl0.75Nb0.25 high-entropy alloy. Our results indicated that the microstructure of the alloy comprised a BCC solid solution phase along with a eutectic mixture of FCC and intermetallic phases. The application of heat treatment resulted in a significant evolution of the microstructure. The precipitation of the needle-like intermetallic phase occurred rapidly with increasing annealing temperature, reaching a maximum proportion at 825 °C, and decreased quickly upon further increase to 1000 °C. Correspondingly, the hardness and compressive yield strength of the alloy increased rapidly, attaining maximum values of approximately 600 HV and 2000 MPa, respectively. However, the precipitation adversely affected magnetic properties. The best values in the as-cast state for saturation magnetization, and coercive force are 0.67 T and 716 A m-1, respectively, while the hardness remains 493 HV. Therefore, it is very suitable for magnetic parts requiring superior mechanical properties.
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