Amorphous Alloy Sheet Material: Advanced Manufacturing Processes, Structural Properties, And Industrial Applications

Compositional Design And Alloy Systems For Amorphous Alloy Sheet Material

The compositional design of amorphous alloy sheet material is critical to achieving the desired glass-forming ability (GFA), mechanical properties, and functional performance. Amorphous alloys are typically multi-component systems that leverage atomic size mismatch, negative heat of mixing, and high configurational entropy to suppress crystallization during cooling 2,5.

Fe-Based Amorphous Alloy Sheet Material

Fe-based amorphous alloys are widely studied for soft magnetic applications due to their high saturation magnetic flux density (Bs > 1.45 T) and low coercivity (Hc < 0.8 Oe) 10. A representative composition includes Fe (55–65 wt%), Co (10–20 wt%), Si (13–17 wt%), and B (8–12 wt%), with glass transition temperature Tg > 800 K and reduced glass transition temperature Tg/Tl > 0.56 10. The addition of cobalt enhances thermal stability and magnetic performance, making these alloys suitable for wireless charging systems and transformer cores where low iron loss is essential 10. Fe-based nanocrystalline soft magnetic materials, derived from amorphous precursors, exhibit an amorphous matrix phase with uniformly distributed nanocrystalline grains (10–20 nm) and fine metal carbide particles, achieving excellent soft magnetic characteristics and workability 13,14.

Zr-Based Amorphous Alloy Sheet Material

Zr-based amorphous alloys, such as Zr-Ni-Cu-Al quaternary systems, are renowned for their high strength (compressive yield strength > 1.5 GPa) and elastic limit (elastic strain ~2%) but suffer from limited ductility at room temperature 12,20. To address this, complex concentrated alloys (CCA) containing refractory elements (Ti, Nb, Ta, Mo) are dispersed within the amorphous matrix, forming a dual-phase microstructure that improves fracture toughness and plastic deformation capability by inducing multiple shear bands and preventing catastrophic crack propagation 12,20. The oxygen content in these composite materials is controlled below 2100 ppm to maintain matrix homogeneity and mechanical integrity 2,5.

Refractory High-Entropy Amorphous Alloy Sheet Material

Refractory high-entropy amorphous alloys comprise three or more refractory metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Re) combined with non-refractory elements (Al, Si, Co, B, Ni) 19. These materials exhibit exceptional high-temperature stability, corrosion resistance in nuclear and chemical environments, and mechanical performance exceeding 1000 MPa tensile strength at elevated temperatures 19. The amorphous structure eliminates grain boundaries, dislocations, and segregation defects inherent in crystalline metals, resulting in uniform stress distribution and enhanced creep resistance 19.

Fe-Te Amorphous Alloy Sheet Material

Fe-Te amorphous alloys, with tellurium content ranging from 14 to 90 atom%, are utilized in optical and magnetic recording applications due to their excellent corrosion resistance, thermal stability, and tunable optical properties 7. These alloys are produced via rapid quenching and exhibit amorphous phase stability up to 400°C, making them suitable for information storage media 7.

Manufacturing Processes And Thickness Control For Amorphous Alloy Sheet Material

The production of amorphous alloy sheet material requires precise control of cooling rates, melt temperature, and substrate conditions to achieve the desired thickness, surface finish, and microstructural uniformity.

Spray Deposition And Rolling For Amorphous Alloy Sheet Material

A novel method for manufacturing thick amorphous alloy sheets involves spray deposition of molten alloy onto a heated sheet base material (200–520°C), followed by immediate rolling while the amorphous film retains plastic flowability 1. This process enables the production of sheets with thicknesses greater than 1 mm and widths exceeding conventional dimensions (typically limited to <100 μm in melt-spinning) 1. The heated substrate prevents premature crystallization and ensures strong metallurgical bonding between the amorphous film and the base material 1. Rolling is performed within a temperature window where the alloy exhibits supercooled liquid behavior (Tg < T < Tx, where Tx is the crystallization onset temperature), allowing thickness reduction without inducing crystallization 1.

Float-Casting Process For Amorphous Alloy Sheet Material

Inspired by float glass manufacturing, the float-casting process involves pouring molten amorphous alloy onto a denser molten metal (e.g., tin or lead) in a controlled atmosphere chamber 3. The amorphous alloy floats on the molten substrate and is cooled at a rate sufficient to avoid traversing the crystalline region in the time-temperature-transformation (TTT) diagram 3. This method produces sheets with "fire-polished" surfaces (surface roughness Ra < 0.1 μm) on both sides, eliminating the need for post-processing grinding or polishing 3. Thickness control is achieved by adjusting the pouring rate, melt viscosity, and cooling rate, enabling sheet thicknesses from 0.5 mm to 5 mm 3.

Conveyor-Based Rapid Solidification For Amorphous Alloy Sheet Material

In conveyor-based processes, molten alloy is poured onto a moving copper or steel belt that rapidly extracts heat, achieving cooling rates of 10⁴–10⁶ K/s 3. The conveyor speed, belt temperature, and melt superheat are optimized to produce continuous amorphous sheets with uniform thickness (±5% variation) and minimal surface defects 3. This method is scalable for industrial production and compatible with in-line annealing or coating processes 3.

Semi-Solid Die-Casting For Amorphous Alloy Sheet Material

Semi-solid die-casting combines smelting and controlled cooling to produce amorphous alloys with 5–8% crystallinity, comprising a nanocrystalline dendritic phase dispersed in an amorphous matrix 11. The master alloy is melted at 950°C under vacuum, then cooled to 810–850°C (semi-solid state) before injection into a die 11. The dendritic phase arrests shear band propagation and induces multiple shear bands, significantly improving plastic deformation capability (plastic strain > 5%) and fracture toughness (KIC > 50 MPa·m^1/2) compared to fully amorphous alloys 11. This method is particularly effective for Zr-based and Ti-based bulk metallic glasses 11.

Pressure-Solidification For Thick Amorphous Alloy Sheet Material

Pressure-solidification involves applying external pressure (>1 atm) during cooling to eliminate casting defects (porosity, shrinkage cavities) and induce residual stress gradients 8. The surface of the amorphous ingot is subjected to higher cooling rates, creating a compressive stress layer (50–200 MPa), while the interior retains tensile stress 8. This stress distribution enhances flexural strength (>2000 MPa) and impact resistance (Charpy impact energy > 50 J) in sheets thicker than 1 mm 8. The method is applicable to Fe-based, Zr-based, and Pd-based amorphous alloys 8.

Microstructural Characteristics And Phase Evolution In Amorphous Alloy Sheet Material

The microstructure of amorphous alloy sheet material is defined by its lack of long-range atomic order, but local atomic arrangements, phase separation, and nanocrystallization can significantly influence properties.

Amorphous Matrix And Short-Range Order

Amorphous alloy sheet material exhibits a disordered atomic structure with short-range order (SRO) extending 0.5–1.5 nm, characterized by icosahedral or trigonal prismatic clusters 2,5. X-ray diffraction (XRD) patterns show broad halos without sharp Bragg peaks, confirming the absence of crystalline phases 2. Transmission electron microscopy (TEM) reveals a featureless, maze-like contrast typical of amorphous materials, with no grain boundaries or dislocations 2,5.

Nanocrystalline Reinforcement In Amorphous Alloy Sheet Material

Amorphous alloy composite materials contain equiaxed crystalline phases (10–50 nm diameter) dispersed in the amorphous matrix, formed via controlled partial crystallization or in-situ precipitation during solidification 2,5. These nanocrystals, often α-Fe, Fe₃Si, or intermetallic compounds, act as reinforcing phases that improve plasticity by promoting shear band multiplication and preventing runaway shear localization 2,5. The oxygen content must be maintained below 2100 ppm to avoid excessive oxide formation, which degrades mechanical properties 2,5.

Dendritic Phase In Semi-Solid Processed Amorphous Alloy Sheet Material

Semi-solid die-casting produces a dendritic crystalline phase (5–8 vol%) embedded in the amorphous matrix 11. The dendrites, typically 1–5 μm in size, form during the semi-solid stage and are retained upon final solidification 11. This dual-phase microstructure enhances toughness by deflecting cracks and distributing strain more uniformly, resulting in compressive plastic strain exceeding 5% and tensile ductility of 2–3% 11.

Residual Stress Distribution In Pressure-Solidified Amorphous Alloy Sheet Material

Pressure-solidification induces a gradient in residual stress, with compressive stress (50–200 MPa) near the surface and tensile stress (20–100 MPa) in the interior 8. This stress profile is measured via X-ray stress analysis or neutron diffraction and correlates with enhanced flexural strength and impact resistance 8. The compressive surface layer inhibits crack initiation, while the tensile interior provides energy absorption during fracture 8.

Mechanical Properties And Performance Metrics Of Amorphous Alloy Sheet Material

Amorphous alloy sheet material exhibits exceptional mechanical properties, including high strength, elastic limit, and hardness, but limited ductility at room temperature.

Tensile And Compressive Strength

Fe-based amorphous alloy sheets exhibit tensile strengths of 2500–3500 MPa and compressive yield strengths of 2000–3000 MPa 10,13. Zr-based amorphous alloys achieve compressive yield strengths exceeding 1800 MPa and tensile strengths of 1500–2000 MPa 12,20. The addition of CCA phases increases fracture toughness (KIC) from 20–30 MPa·m^1/2 (monolithic amorphous) to 50–80 MPa·m^1/2 (composite) 12,20.

Elastic Modulus And Elastic Limit

Amorphous alloy sheet material exhibits elastic moduli ranging from 80 GPa (Zr-based) to 180 GPa (Fe-based), with elastic strain limits of 1.5–2.5% 10,12. This high elastic limit enables energy storage applications, such as springs and flexures, where large reversible deformation is required 12.

Hardness And Wear Resistance

Vickers hardness values for amorphous alloy sheets range from 500 HV (Zr-based) to 1200 HV (Fe-based), significantly higher than crystalline steels (200–400 HV) 10,13. The absence of grain boundaries and dislocations results in superior wear resistance, with wear rates 10–100 times lower than conventional alloys under dry sliding conditions 13.

Flexural Strength And Impact Resistance

Pressure-solidified amorphous alloy sheets thicker than 1 mm exhibit flexural strengths exceeding 2000 MPa and Charpy impact energies greater than 50 J, attributed to the compressive surface stress layer and elimination of casting defects 8. These properties make thick amorphous sheets suitable for structural applications requiring high load-bearing capacity and damage tolerance 8.

Magnetic Properties And Soft Magnetic Performance Of Amorphous Alloy Sheet Material

Fe-based amorphous alloy sheet material is widely used in soft magnetic applications due to its high saturation magnetic flux density, low coercivity, and low core loss.

Saturation Magnetic Flux Density And Coercivity

Fe-Co-Si-B amorphous alloys exhibit saturation magnetic flux densities (Bs) exceeding 1.45 T, comparable to silicon steel but with significantly lower coercivity (Hc < 0.8 Oe vs. 5–10 Oe for silicon steel) 10. The low coercivity results from the absence of grain boundaries and magnetocrystalline anisotropy, enabling efficient magnetization reversal and reduced hysteresis loss 10.

Core Loss And Permeability

Amorphous alloy sheets exhibit core losses of 0.1–0.3 W/kg at 1 T and 50 Hz, 70–80% lower than silicon steel (1.0–1.5 W/kg) 10,17. Relative permeability (μr) ranges from 10,000 to 100,000 at low frequencies, decreasing to 1,000–5,000 at 1 MHz due to eddy current effects 9,17. Laminated structures with electrically insulating coatings (e.g., lead-free glass with softening point < 500°C) further reduce eddy current losses and improve high-frequency performance 17.

Nanocrystalline Soft Magnetic Amorphous Alloy Sheet Material

Controlled annealing of Fe-Si-B-P-Cu amorphous precursors at 500–600°C for 1–2 hours induces the precipitation of α-Fe(Si) nanocrystals (10–20 nm) in the amorphous matrix, forming nanocrystalline soft magnetic materials 14. These materials exhibit Bs > 1.6 T, Hc < 0.5 Oe, and core losses < 0.1 W/kg at 1 T and 50 Hz, outperforming both amorphous and crystalline alloys 14. The fine nanocrystalline structure reduces magnetostriction and enhances permeability, making these materials ideal for high-efficiency transformers and inductors 14.

Electromagnetic Wave Absorption

Amorphous soft magnetic alloy powders, flattened into sheet form, exhibit high magnetic permeability (μr > 50) and loss tangent (tan δ > 0.3) in the 1–10 GHz range, enabling effective electromagnetic wave absorption 4,9. The flattened powder morphology (aspect ratio 5–10) enhances shape anisotropy and improves impedance matching with free space 4,9. These sheets are used in electromagnetic interference (EMI) shielding and noise suppression applications in consumer electronics 4,9.

Thermal Stability And Glass-Forming Ability Of Amorphous Alloy Sheet Material

The thermal stability and glass-forming ability (GFA) of amorphous alloy sheet material determine the processing window and long-term structural integrity.

Glass Transition And Crystallization Temperatures

Fe-based amorphous alloys exhibit glass transition temperatures (Tg) of 500–600°C and crystallization onset temperatures (Tx) of 550–650°C, providing a supercooled liquid region (ΔTx = Tx - Tg) of 30–60 K 10,13. Zr-based amorphous alloys have Tg of 350–450°C and Tx of 450–550°C, with ΔTx of 50–100 K, enabling thermoplastic forming in the supercooled liquid state 12,20. Refractory high-entropy amorphous alloys exhibit Tg > 600°C and Tx > 700°C, maintaining amorphous structure up to 800