Recent advancements in the synthesis of Co31.5Cr7Fe30Ni31.5 high-entropy alloy (HEA) powders have demonstrated exceptional control over microstructural homogeneity and phase stability. Utilizing gas atomization techniques, researchers achieved a powder size distribution of 10-45 µm with a spherical morphology yield of 92.3%. X-ray diffraction (XRD) analysis confirmed a single-phase face-centered cubic (FCC) structure with a lattice parameter of 3.59 Å, while energy-dispersive spectroscopy (EDS) mapping revealed elemental homogeneity with less than 1.5% deviation across the powder particles. This precision in synthesis is critical for additive manufacturing applications, where powder quality directly impacts mechanical properties.
The mechanical performance of Co31.5Cr7Fe30Ni31.5 HEA powders has been rigorously evaluated under extreme conditions. Compression tests at room temperature revealed a yield strength of 850 MPa and an ultimate tensile strength of 1,250 MPa, with an elongation to fracture of 18%. High-temperature testing at 800°C showed remarkable retention of strength, with a yield strength of 620 MPa and a fracture toughness of 95 MPa√m. These results surpass those of conventional Ni-based superalloys, positioning this HEA as a promising candidate for aerospace and energy applications where thermal stability and mechanical integrity are paramount.
Thermodynamic modeling and experimental validation have provided insights into the phase stability and oxidation resistance of Co31.5Cr7Fe30Ni31.5 HEA powders. CALPHAD-based simulations predicted the formation of a stable FCC phase up to 1,200°C, which was corroborated by differential scanning calorimetry (DSC) showing no phase transitions below this temperature. Oxidation tests at 900°C in air revealed a parabolic rate constant of 2.3 × 10⁻¹⁴ g²/cm⁴s, significantly lower than that of Inconel 718 (1.8 × 10⁻¹³ g²/cm⁴s). The formation of a protective Cr₂O₃ layer was identified as the primary mechanism for enhanced oxidation resistance.
Additive manufacturing studies using selective laser melting (SLM) have demonstrated the feasibility of fabricating dense Co31.5Cr7Fe30Ni31.5 HEA components with minimal defects. Optimized processing parameters included a laser power of 300 W, scan speed of 800 mm/s, and layer thickness of 30 µm, resulting in a relative density of 99.2%. Microstructural analysis revealed fine equiaxed grains with an average size of 8 µm, contributing to improved hardness (HV₀.₅ = 320) and wear resistance (wear rate = 2.1 × 10⁻⁵ mm³/Nm). These findings highlight the potential for leveraging advanced manufacturing techniques to unlock new applications for HEAs.
The electrochemical behavior of Co31.5Cr7Fe30Ni31.5 HEA powders in corrosive environments has been investigated to assess their suitability for marine and chemical processing industries. Potentiodynamic polarization tests in a 3.5 wt% NaCl solution revealed a corrosion potential (E_corr) of -0.25 V vs SCE and a corrosion current density (i_corr) of 0.12 µA/cm², outperforming stainless steel AISI 304 (E_corr = -0 Mg-6Gd-3Y-Zr alloy powders for additive manufacturing"
Recent advancements in the synthesis of Mg-6Gd-3Y-Zr alloy powders have demonstrated exceptional potential for additive manufacturing (AM) applications. High-purity powders with a particle size distribution of 15–53 µm were produced via gas atomization, achieving a sphericity index of 0.92 ± 0.03, which is critical for flowability and layer uniformity in AM processes. The alloy composition, comprising 6 wt% Gd, 3 wt% Y, and 0.5 wt% Zr, was optimized to enhance mechanical properties while maintaining lightweight characteristics. X-ray diffraction (XRD) analysis confirmed the presence of Mg5(Gd,Y) intermetallic phases, which contribute to precipitation strengthening. Compression tests revealed a yield strength of 220 MPa and an ultimate tensile strength (UTS) of 320 MPa, outperforming conventional magnesium alloys by ~30%. These results underscore the suitability of Mg-6Gd-3Y-Zr powders for high-performance AM components.
The thermal stability and microstructural evolution of Mg-6Gd-3Y-Zr alloy during selective laser melting (SLM) were investigated using in-situ synchrotron radiation imaging. The study revealed that the cooling rate of ~10^6 K/s during SLM resulted in a fine-grained microstructure with an average grain size of 2.8 µm. Electron backscatter diffraction (EBSD) analysis showed a strong basal texture with a maximum intensity of 12.7 multiples of random distribution (MRD), which significantly influences anisotropic mechanical behavior. Post-processing heat treatment at 500°C for 2 hours led to the precipitation of nanoscale β' phases (Mg5(Gd,Y)), increasing hardness from 85 HV to 110 HV. Thermal conductivity measurements indicated a value of 65 W/m·K at room temperature, making it suitable for heat dissipation applications in aerospace and automotive industries.
Corrosion resistance is a critical factor for Mg-based alloys in practical applications. Electrochemical testing in a 3.5 wt% NaCl solution demonstrated that Mg-6Gd-3Y-Zr alloy exhibited a corrosion current density (Icorr) of 1.2 µA/cm², significantly lower than that of pure Mg (15 µA/cm²). The formation of a protective oxide layer enriched with Gd and Y was confirmed by X-ray photoelectron spectroscopy (XPS), which reduced the corrosion rate by ~92%. Additionally, immersion tests over 30 days showed a weight loss rate of only 0.12 mg/cm²/day, highlighting its potential for marine environments.
The recyclability and sustainability aspects of Mg-6Gd-3Y-Zr alloy powders were evaluated through multiple re-melting cycles using vacuum induction melting (VIM). After five cycles, the alloy retained >95% of its original mechanical properties, with minimal compositional deviation (<1%). Life cycle assessment (LCA) revealed that the production process emitted only 8 kg CO2/kg alloy, compared to ~20 kg CO2/kg for traditional aluminum alloys. This positions Mg-6Gd-3Y-Zr as an environmentally friendly alternative for AM applications.
Finally, the integration of machine learning algorithms for process optimization in AM has been explored to enhance the performance of Mg-6Gd-3Y-Zr components. A neural network model trained on experimental data predicted optimal laser power (250 W), scan speed (800 mm/s), and layer thickness (30 µm) with an accuracy of >95%. This approach reduced porosity levels to <0.5% and improved UTS by ~15%, demonstrating the synergy between advanced materials and computational techniques.
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