Description of Aerospace Alloy Sheet Products:

1. High-Strength Alloy Structural Steel Sheet: The Cornerstone of Strength
2. Core Product Performance: This type of material achieves ultra-high strength through phase transformation strengthening (martensite obtained by quenching) and secondary hardening (carbide precipitation during tempering). Its peak performance is reflected in the triangular balance of strength, toughness, and fatigue life.
3. Microstructure: Based on tempered martensite to ensure high strength; high toughness is achieved through strict control of austenite grain size and impurity elements.
4. Key Indicators: In addition to tensile strength (1.8-2.2GPa), fracture toughness (K₁C) and fatigue crack growth rate (da/dN) are more critical indicators for measuring its safe service life.
5. Process Determinism: Performance highly depends on vacuum melting (VIM/VAR) to control impurities and precise multi-stage heat treatment processes. Any deviation may lead to a catastrophic increase in stress corrosion cracking sensitivity.
6. Engineering Positioning: It is the core load-bearing material under the concept of aircraft safe life design. Choosing it means placing absolute static strength and reliability above weight and cost.
7. Superalloy Sheet: Guardians in the Flames
8. Core Product Performance: Relying on solid solution strengthening (W, Mo, etc.) and precipitation strengthening (γ' phase - Ni₃(Al, Ti)). Its core challenge is to resist creep (slow plastic deformation) and thermo-mechanical fatigue at temperatures close to the alloy's melting point.
9. Microstructure: Coherently ordered γ' phases are uniformly distributed on the austenitic matrix. The quantity, size, and stability of the phases directly determine the high-temperature performance.
10. Key Indicators: Creep rupture strength (such as 1000-hour fracture stress) and creep limit are direct bases for designing engine hot-end components. Oxidation resistance is ensured by a dense oxide film formed by elements such as Cr and Al.
11. Process Specificity: Directional solidification or single crystal casting technology is used to eliminate transverse grain boundaries, significantly improving the temperature-bearing capacity. For sheet, precise control of rolling and heat treatment processes is required to optimize the microstructure.
12. Engineering Positioning: It is a bottleneck material for improving thrust-to-weight ratio and thermal efficiency, and its performance progress directly determines the birth of a new generation of engines.
13. Titanium Alloy Sheet: Lightweight and Versatile
14. Core Product Performance: Realizing diversified performance matching through α+β dual-phase microstructure regulation. Its high specific strength stems from the combination of strong covalent bonds between titanium atoms and the close-packed hexagonal/body-centered cubic structure.
15. Microstructure Regulation: For α+β alloys such as Ti-6Al-4V, equiaxed microstructure (high plasticity), bimodal microstructure (good comprehensive performance), or basketweave microstructure (high fracture toughness, creep resistance) can be obtained by changing β-zone processing and heat treatment.
16. Key Characteristics: Excellent corrosion resistance comes from the dense, self-healing TiO₂ oxide film formed on the surface. Its relatively low elastic modulus helps reduce stress concentration, but attention must be paid to springback during processing.
17. Compatibility Advantage: It has good electrochemical compatibility with polymer matrix composites, avoiding the galvanic corrosion problem when in contact with aluminum alloys, making it an ideal choice for hybrid structures (Metal-Composite).
18. Engineering Positioning: It is irreplaceable in key parts where the weight reduction benefit far exceeds its cost, and it is a bridge between "high-strength steel" and "composites" in terms of performance and cost.
19. Aluminum Alloy Sheet: A Classic and Efficient Choice
20. Core Product Performance: Strengthening is achieved through solution-precipitation strengthening (such as θ' phase in Al-Cu series, η' phase in Al-Zn-Mg-Cu series). Its performance optimization focuses on the balance of static strength, fatigue performance, damage tolerance, and corrosion resistance.
21. Key Process: Cladding aluminum process (coating a thin layer of pure aluminum on the surface of the sheet) is a sacrificial anode protection, which is key to significantly improving stress corrosion resistance.
22. Performance Trade-Off: Generally, the higher the strength (such as 7075-T6), the lower the corrosion resistance and damage tolerance. Therefore, over-aged states such as T77 have been developed, which greatly improve stress corrosion resistance and fracture toughness at the expense of a small amount of strength.
23. Engineering Positioning: In mainstream airframe structures below 150°C, it provides unparalleled comprehensive advantages in performance, cost, and process maturity, and is the constituent material of the aircraft "trunk".