Aluminum 7075

Aluminum 7075 is a high-strength aluminum alloy ideal for CNC machining of aerospace, defense, and automotive parts requiring exceptional strength, wear resistance, and fatigue performance.

Introduction to Aluminum 7075

Aluminum 7075 is a high-strength, heat-treatable aluminum alloy that delivers exceptional mechanical performance and fatigue resistance, especially in the aerospace and automotive industries. Known for its excellent strength-to-weight ratio, 7075 outperforms most other aluminum grades in structural applications requiring durability under dynamic loading.

Thanks to its machinability and superior hardness in T6 and T73 tempers, Aluminum 7075 is ideal for CNC machining of high-performance parts such as tooling, frames, suspension components, and military-grade equipment.

Chemical, Physical, and Mechanical Properties of Aluminum 7075

Chemical Composition (Typical)

Element	Composition Range (wt.%)	Key Role
Aluminum (Al)	Balance	Lightweight base with corrosion resistance
Zinc (Zn)	5.1–6.1	Primary strengthening element through precipitation hardening
Magnesium (Mg)	2.1–2.9	Improves strength and hardness
Copper (Cu)	1.2–2.0	Increases hardness and wear resistance
Chromium (Cr)	0.18–0.28	Enhances corrosion resistance and toughness
Iron (Fe)	≤0.50	Residual element
Silicon (Si)	≤0.40	Residual element
Manganese (Mn)	≤0.30	Residual element
Titanium (Ti)	≤0.20	Grain refining element

Physical Properties

Property	Value (Typical)	Test Standard/Condition
Density	2.81 g/cm³	ASTM B311
Melting Point	477–635°C	ASTM E299
Thermal Conductivity	130 W/m·K at 25°C	ASTM E1952
Electrical Conductivity	33% IACS at 20°C	ASTM B193
Coefficient of Expansion	21.2 µm/m·°C	ASTM E228
Specific Heat Capacity	960 J/kg·K	ASTM E1269
Elastic Modulus	71.7 GPa	ASTM E111

Mechanical Properties (T6/T73 Temper)

Property	Value (Typical)	Test Standard
Tensile Strength	510–570 MPa (T6)	ASTM E8/E8M
Yield Strength (0.2%)	430–505 MPa (T6)	ASTM E8/E8M
Elongation	≥7% (T6), ≥11% (T73)	ASTM E8/E8M
Hardness	150–175 HB	ASTM E10
Fatigue Strength	160 MPa (T6)	ASTM E466
Impact Resistance	High (T73)	ASTM E23

Key Characteristics of Aluminum 7075

High Strength-to-Weight Ratio: Aluminum 7075 offers one of the highest tensile strengths among aluminum alloys, enabling weight savings without sacrificing load-bearing capacity. It is ideal for aerospace structural members and high-speed moving assemblies.

Excellent Fatigue Resistance: Especially in the T6 temper, 7075 is designed to resist crack propagation under repeated stress—making it suitable for wings, gearboxes, and high-cycle mechanical components.

Moderate Corrosion Resistance: While not as corrosion-resistant as 6061 or 6063, 7075 responds well to anodizing or alodine coating for additional protection in marine or humid environments.

Dimensional Stability and Wear Resistance: Its hardness and strength reduce deflection and tool wear, maintaining tolerances of ±0.005 mm in CNC machined parts with minimal distortion during thermal cycling.

Low Formability but Excellent Machinability: Although not ideal for deep bending or forming, 7075 machines cleanly and quickly with carbide tools, enabling efficient production of high-precision parts.

CNC Machining Challenges and Solutions for Aluminum 7075

Machining Challenges

High Hardness: Accelerates tool wear compared to softer aluminum alloys.
Work Hardening: Requires consistent cutting to avoid localized hard zones.
Thermal Sensitivity: Generates heat quickly, necessitating proper cooling during deep cuts.

Optimized Machining Strategies

Tool Selection

Parameter	Recommendation	Rationale
Tool Material	Micrograin or coated carbide	Resists edge wear and retains sharpness
Geometry	Neutral to high rake angle	Balances strength and chip evacuation
Cutting Speed	150–250 m/min (T6)	Prevents overheating and tool breakdown
Feed Rate	0.08–0.20 mm/rev	Maintains chip thickness and tool longevity
Coolant	High-pressure flood or mist	Reduces thermal deformation and ensures clean finish

Aluminum 7075 Cutting Parameters (ISO 513 Compliance)

Operation	Speed (m/min)	Feed (mm/rev)	Depth of Cut (mm)	Coolant Pressure (bar)
Roughing	150–200	0.15–0.20	2.0–4.0	30–50 (Flood)
Finishing	200–250	0.05–0.10	0.2–1.0	50–80 (Mist/Flood)

Surface Treatment for Aluminum 7075 CNC Parts

Anodizing: Type II and hard anodizing improve corrosion resistance and surface hardness, though color uniformity may vary.
Powder Coating: Adds impact-resistant protective layer with good chemical stability for outdoor or rugged parts.
Electropolishing: Enhances appearance and corrosion protection for critical aerospace hardware.
Passivation: Reduces residual contaminants and restores oxide integrity after machining.
Brushing: Provides matte or satin finishes, ideal for high-touch components and visibility-critical surfaces.
Alodine Coating: Provides conductive, corrosion-resistant finish without dimensional impact. It is widely used in aviation.
UV Coating: Fast-curing transparent layer for chemical resistance and finish durability in consumer electronics.
Lacquer Coating: Protects and polishes machined aluminum surfaces in tools, optics, and mechanical housings.