Differences in aluminum content in aluminum alloys: How do they influence core performance such as product strength and corrosion resistance?

HW-A. Benchmark Classification and Detection Logic of Aluminum Content in Aluminum Alloys

A. Differences in Aluminum Content Gradients Across Multiple Standard Systems

The classification of aluminum content in aluminum alloys is not globally unified, and precise definition must consider the applicability differences of various standard systems. The core differences between China’s GB/T 3190-2022 (replacing the 1996 version), ASTM B209-23, and EN 573-3:2019 lie in the high-purity range and allowable deviation:

Note: Data is synthesized from the original texts of GB/T 3190-2022, ASTM B209-23, and EN 573-3:2019. Such differences directly affect quality control in cross-border procurement. For example, when an automotive component enterprise adopts ASTM 6061-T6, it needs to increase the lower limit of aluminum content control by 0.3% to meet performance requirements.

B.Precision Grading and Application Scenarios of Detection Technologies

In actual production, a combined scheme of “LIBS real-time monitoring + GDMS periodic calibration” is required. A CHINALCO base has controlled the fluctuation of aluminum content within ±0.07% through this model.

HW-B. Regulation Mechanism of Aluminum Content on Core Properties (In-Depth Supplement)

A. Strength Performance: Kinetic Mechanism of Precipitated Phase Evolution

The strengthening of 7xxx series alloys essentially relies on the ordered evolution of precipitated phases during aging. Taking Alloy 7075 (87% Al) as an example:

1. Supersaturated Solid Solution (SSS) Stage (after quenching): Zn and Mg atoms are uniformly distributed in the aluminum matrix, with a strength of only 200MPa;

2. GP Zone Formation Stage (120℃×2h): Atomic clusters with size ≤5nm form, increasing strength to 450MPa;

3. η’ Phase Precipitation Stage (120℃×12h): Acicular precipitated phases (aspect ratio 10:1) with spacing ≤10nm form, reaching a strength of 572MPa (T6 temper);

4. η Phase Transformation Stage (120℃×24h): η’ phases coarsen into η phases (MgZn₂), reducing strength to 550MPa.

By fine-tuning aluminum content (e.g., Alloy 7050 with 88.3%-89.5% Al), the transformation time of η phases can be delayed, extending the duration of peak strength by 30% to meet the long-term service requirements of aerospace components.

B. Corrosion Resistance: Electronic Structure Regulation of Oxide Films

The Al₂O₃ film of 1xxx series pure aluminum has a hexagonal crystal structure with a band gap of 6.2eV, which can effectively block electron transfer. In contrast, the MgO-Al₂O₃ composite film formed by Alloy 5A05 (94.5%-95.2% Al) has a spinel structure, with the band gap reduced to 5.8eV, but the defect state density decreases from 10¹⁷cm⁻³ to 10¹⁵cm⁻³, maintaining the breakdown potential above 1.4V vs SCE. XPS depth profiling shows that Mg elements in the composite film exhibit a gradient distribution (Mg/O ratio 0.3 in the surface layer and 0.1 in the inner layer), which can buffer the penetration driving force of Cl⁻ ions.

C. Newly Added: Dependence of Thermophysical Properties on Aluminum Content

Aluminum content directly affects the thermal conductivity and thermal expansion characteristics of alloys:

• Pure aluminum 1060 (99.6% Al) has a thermal conductivity of 237W/(m·K) and a thermal expansion coefficient of 23.1×10⁻⁶/℃, suitable for heat dissipation substrates;

• Alloy 6061 (95.8%-98.6% Al) has a reduced thermal conductivity of 167W/(m·K) and a thermal expansion coefficient of 23.0×10⁻⁶/℃, meeting the thermal matching requirements of structural components;

• Alloy 7075 (87% Al) has a thermal conductivity of only 130W/(m·K), requiring composite heat dissipation structures to compensate for thermal management capabilities.

HW-C. Application-Oriented Aluminum Content Selection Strategy (Newly Added Cutting-Edge Fields)

HW-D. Production Technology Bottlenecks and Breakthrough Paths for Precise Aluminum Content Control (Newly Added Smart Manufacturing Module)

A. Core Technology Bottlenecks (Supplemented Details)

1. Non-Linear Interference of Impurity Elements: For every 0.01% increase in Fe content, the detected aluminum content of 1xxx series alloys decreases by 0.008%. This is because the Al₃Fe phase formed by Fe and Al cannot be completely dissociated in electrolysis, requiring ICP-MS to pre-calibrate impurity correction factors.

2. Composition Segregation During Solidification: During continuous casting of 7xxx series alloys, the columnar crystal growth rate reaches 15mm/min, resulting in a 2.3% higher Zn content at grain boundaries than in the center, indirectly causing a 1.8% difference in aluminum content. Dynamic soft reduction technology (reduction amount 0.3mm/s) is needed to suppress segregation.

B. Breakthrough Paths (Newly Added Smart Manufacturing Technologies)

1. Digital Twin Casting System: A leading aluminum enterprise has built a digital twin casting model that integrates real-time data from 128 sensors. It can predict the fluctuation trend of molten aluminum composition (30 minutes in advance), increasing the yield of 7xxx series alloys from 88% to 95%. By coupling heat transfer-mass transfer-solidification kinetics equations, the system realizes adaptive adjustment of alloy material addition (adjustment precision 0.02kg/ton of molten aluminum).

2. New High-Purity Aluminum Refining Technology: The combined process of three-layer liquid electrolysis + vacuum distillation can purify 4N high-purity aluminum (99.99% Al) to 5N grade (99.999% Al), reducing the total impurity content from 100ppm to below 10ppm, which meets the requirements of semiconductor bonding wires.

HW-E. Conclusion: The Art of Precise Balance of Aluminum Content

The core of aluminum alloy performance regulation is to establish a four-dimensional mapping relationship between “aluminum content – alloying elements – process parameters – service performance”. Future breakthrough points include:

1. Atomic-Level Composition Design: Optimize the 7xxx series Al-Zn-Mg-Cu-Sc system through first-principles calculations, narrowing the aluminum content control window to ±0.2%, to achieve a tensile strength exceeding 650MPa while maintaining a fatigue life ≥10⁸ cycles;

2. Green Refining Technology: Develop chromium-free passivation processes for 5xxx series alloys (96%-97% Al), reducing wastewater treatment costs by 40% while maintaining corrosion resistance;

3. Intelligent Closed-Loop Control: Realize millisecond-level response of LIBS detection – AI prediction – robotic adjustment, targeting to control aluminum content fluctuation within ±0.05% to meet the “zero-defect” manufacturing requirements of the aerospace industry.