Precision Engineering and Dimensional Stability of Aluminum 7175 Sheet

In the aerospace and high-performance engineering sectors, precision and stability are not just desired — they are mandatory. Materials used for aircraft structures must maintain exact dimensional tolerances and resist deformation even under extreme mechanical and thermal stresses. One alloy that consistently meets these challenges is Aluminum 7175 Sheet, a high-strength, heat-treatable aluminum alloy designed for applications where accuracy, consistency, and reliability are essential.

At SASAALUMINUM, the production of Aluminum 7175 Sheets is driven by precision engineering and stringent quality control at every stage — from melting and rolling to heat treatment and final inspection. The result is a product that combines exceptional dimensional stability, strength, and surface integrity, making it ideal for use in aerospace, defense, and precision manufacturing industries.

This article explores how SASAALUMINUM achieves outstanding dimensional accuracy and stability in Aluminum 7175 Sheets, along with the advanced engineering techniques that ensure superior performance in demanding environments.

Overview of Aluminum Alloy 7175

Aluminum 7175 is part of the 7xxx series (Al-Zn-Mg-Cu alloys), known for high strength-to-weight ratios and superior fatigue resistance. Developed as an improved variant of 7075, Aluminum 7175 offers enhanced fracture toughness and better stress-corrosion resistance, making it ideal for aircraft-grade applications.

Typical Chemical Composition (%):

• Zinc (Zn): 5.6–6.1

• Magnesium (Mg): 2.0–2.5

• Copper (Cu): 1.2–1.6

• Chromium (Cr): 0.18–0.25

• Aluminum (Al): Balance

These alloying elements allow Aluminum 7175 to achieve exceptional mechanical performance through precipitation hardening. Its typical tensile strength ranges between 560–600 MPa, offering both high load-bearing capacity and excellent fatigue resistance.

At SASAALUMINUM, every batch of 7175 alloy is carefully engineered to maintain strict compositional accuracy, ensuring predictable performance during heat treatment and forming.

Importance of Precision Engineering in Aerospace Materials

Precision engineering refers to the practice of maintaining exact dimensional tolerances, surface finishes, and mechanical uniformity throughout manufacturing. In the aerospace industry, even micrometer-level deviations can cause assembly issues or structural imbalance.

For aircraft-grade materials like Aluminum 7175, precision is vital because:

1. Aircraft Components Require Exact Fit: Tight tolerances ensure seamless integration of panels, skins, and fittings.

2. Dimensional Stability Reduces Maintenance: Components that resist deformation perform reliably over long service lives.

3. Thermal Expansion Control: Stable alloys minimize warping during flight or temperature variation.

4. Fatigue Life Improvement: Uniform microstructure reduces stress concentrations and crack initiation points.

That’s why SASAALUMINUM emphasizes dimensional accuracy and metallurgical consistency in every sheet of Aluminum 7175 produced.

The Engineering Challenges of Dimensional Stability

Dimensional stability is the ability of a material to retain its original shape and dimensions under stress, heat, or mechanical processing. For Aluminum 7175, achieving stability requires controlling multiple variables:

• Residual Stress: Introduced during rolling or machining; can cause warping if not properly relieved.

• Thermal Expansion: High-temperature processing can change dimensions if cooling is not uniform.

• Microstructural Uniformity: Uneven grain size or precipitate distribution can lead to localized deformation.

• Elastic Recovery: During machining or forming, internal stress may cause “springback” effects.

To overcome these challenges, SASAALUMINUM employs advanced precision rolling, heat treatment, and mechanical flattening technologies to achieve consistent dimensional stability across every batch of Aluminum 7175 Sheets.

SASAALUMINUM’s Advanced Manufacturing Approach

The manufacturing process at SASAALUMINUM is meticulously designed to ensure high dimensional accuracy and long-term stability of Aluminum 7175 Sheets.

1. Controlled Alloy Melting

• Melting is performed in vacuum induction furnaces to maintain purity and prevent gas entrapment.

• Precise ratios of zinc, magnesium, copper, and chromium are monitored using spectrographic analysis.

• The molten alloy undergoes argon degassing to eliminate hydrogen and prevent porosity.

This ensures a homogeneous composition — the foundation for stable mechanical and dimensional properties.

2. Homogenization Heat Treatment

Before rolling, cast ingots are homogenized at 470°C–480°C for up to 24 hours.

• Dissolves segregated alloying elements.

• Eliminates internal stresses.

• Produces a uniform microstructure ready for deformation.

This step is critical to achieving even grain growth during rolling and improving dimensional control.

3. Precision Rolling Process

SASAALUMINUM utilizes automated multi-stand rolling mills equipped with advanced Automatic Gauge Control (AGC) systems.

Key Process Features:

• Temperature controlled between 420°C and 450°C for hot rolling.

• Real-time thickness monitoring with laser sensors.

• Computer-controlled cooling rates to maintain uniform deformation.

Each pass through the mill is precisely calculated to achieve the desired sheet thickness while maintaining straightness and flatness.

After rolling, the sheets are cooled in a controlled environment to prevent warping and residual stress buildup.

4. Stress-Relief Annealing and Aging

To ensure long-term dimensional stability, Aluminum 7175 Sheets undergo specific heat treatment cycles depending on the desired temper:

T6 Temper:

• Solution heat-treated at 475°C, water quenched, then artificially aged at 120°C for 24 hours.

• Provides maximum strength but moderate stress-corrosion resistance.

T73 and T74 Tempers:

• Overaged for improved stress-corrosion and dimensional stability.

• Ensures reduced residual stress and improved long-term reliability.

All heat treatment processes at SASAALUMINUM are performed in computer-controlled furnaces with temperature accuracy of ±2°C, ensuring uniform precipitation and microstructural balance.

5. Precision Leveling and Flattening

After heat treatment, each sheet undergoes tension leveling — a process that stretches the sheet slightly beyond its yield point to relieve internal stress and ensure perfect flatness.

This ensures that SASAALUMINUM Aluminum 7175 Sheets remain dimensionally stable during machining, forming, and assembly, minimizing springback or distortion.

Ensuring Dimensional Accuracy

To achieve the precise tolerances required for aerospace applications, SASAALUMINUM employs advanced measurement and control technologies:

• Laser Thickness Measurement: Monitors sheet gauge continuously during rolling.

• Coordinate Measuring Machines (CMM): Verify dimensional accuracy and planarity.

• Flatness Testing: Ensures maximum deviation ≤0.5 mm/m.

• Surface Roughness Inspection: Confirms Ra ≤ 0.8 µm for aerospace-grade finishing.

All measurements are digitally recorded and linked to each batch number for full traceability and quality documentation.

Surface Integrity and Finishing

Dimensional accuracy must be complemented by superior surface integrity, especially for aerospace components that undergo bonding, anodizing, or coating.

SASAALUMINUM’s finishing capabilities include:

• Precision Grinding and Polishing: Removes rolling marks and ensures mirror-flat surface.

• Anodizing and Conversion Coating: Enhances corrosion resistance without altering dimensions.

• Chemical Cleaning: Eliminates oxides and ensures perfect bonding surfaces.

These treatments ensure the sheets meet both structural and aesthetic requirements while maintaining dimensional integrity.

Testing and Quality Verification

Every Aluminum 7175 Sheet undergoes rigorous testing according to international aerospace standards to verify dimensional and mechanical stability.