7075 Aluminum Alloy CNC Machining Material Handbook

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Material Quick Reference Card

┌──────────────────────────────────────────────┐
│ Material Name: 7075 Aluminum Alloy
│ Category: Al-Zn-Mg-Cu high-strength aluminum alloy
│ Density: 2.81 g/cm³
│ Tensile Strength: 500–570 MPa
│ Yield Strength: 430–505 MPa
│ Hardness: 140–160 HB
│ Melting Point: 477–635 ℃
│ Machinability: ★★★★☆ Good
│ Corrosion Resistance: ★★★☆☆ Moderate
│ Cost: ★★★★☆ High
│ Keywords: high strength, aerospace, lightweight, T651
└──────────────────────────────────────────────┘

1. Material Overview

1.1 Basic Introduction

7075 aluminum alloy is one of the strongest common aluminum alloys. It is used when high strength-to-weight ratio is required, especially in aerospace, robotics, motorsport, precision fixtures, and high-load lightweight structures.

In CNC machining, 7075 Aluminum Alloy should be evaluated by strength, stiffness, corrosion resistance, machinability, tolerance stability, surface treatment compatibility, cost, and production volume.

1.2 Source, Production, and Raw Stock Forms

Produced from refined aluminum alloyed with zinc, magnesium, and copper. CNC stock is usually supplied as T6 or T651 plate, bar, and forged block.

Common CNC raw material forms include round bar, square bar, plate, sheet, tube, extrusion, forging, casting, and custom blank. The best form depends on part geometry, required tolerance, mechanical properties, and order quantity.

2. Composition and Physical Properties

2.1 Chemical Composition and Grade System

2.2 Physical Properties

3. Mechanical and Chemical Performance

3.1 Mechanical Properties

Mechanical values vary with standard, heat treatment, product form, section thickness, and supplier certificate. For safety-critical parts, use certified material data instead of generic values.

3.2 Corrosion Resistance

Corrosion performance depends on alloy chemistry, environment, surface roughness, heat treatment, and protective finish. For outdoor, marine, chemical, medical, or high-humidity applications, confirm the required material grade and finishing process before machining.

3.3 Special Properties

Important special properties may include heat-treatment response, magnetic behavior, conductivity, weldability, high-temperature resistance, low-temperature toughness, biocompatibility, or environmental compliance. These should be reviewed according to the exact grade and application.

4. CNC Machining Process

4.1 Machinability Evaluation

Machinability rating: ★★★★☆ Good.

The machining strategy should consider material hardness, ductility, thermal conductivity, work-hardening tendency, chip shape, and tool wear behavior.

4.2 Recommended Tooling

Use rigid workholding, sharp tools, stable tool overhang, and suitable carbide tooling. For non-ferrous metals, polished flutes and high rake angles often improve chip evacuation. For steels, stainless steels, titanium, and nickel alloys, coating choice and coolant delivery are critical for tool life.

4.3 Reference Cutting Parameters

These values are starting references only. Final parameters should be adjusted according to tool diameter, machine rigidity, coolant, clamping, tolerance, and surface finish requirements.

4.4 Cooling and Lubrication

Use coolant strategy according to material behavior. Flood coolant is common for steels, stainless steels, titanium, and nickel alloys. Air blast or mist can be useful for aluminum and brass. Magnesium requires strict fire-safety controls for chips and dust.

4.5 Machining Challenges and Solutions

4.6 Chip Control

Stable chip evacuation protects surface finish, improves tool life, and reduces dimensional variation. Chip form should be controlled by tool geometry, feed per tooth, depth of cut, coolant direction, and toolpath strategy.

5. Post-Processing and Finishing

5.1 Surface Treatment Options

Hard anodizing, chromate conversion, painting, nickel plating.

Typical CNC surface roughness can range from Ra 3.2 μm for general machining to Ra 0.8 μm or better with finishing passes, polishing, grinding, or lapping where applicable.

5.2 Heat Treatment

T6 and T651 are common. T651 is preferred for CNC plates because stress-relief stretching improves dimensional stability.

6. Applications and Material Selection

6.1 Typical Applications

6.2 Advantages and Limitations

6.3 Cost and Selection Advice

Relative material cost: ★★★★☆ High.

Choose 7075 Aluminum Alloy when its strength, corrosion resistance, machining behavior, surface finish, and cost match the part requirements. Compare it with nearby grades before final selection, especially when the design involves tight tolerance, harsh environment, heat treatment, welding, or high-volume production.