Common Aluminum Alloys Used in CNC Machining

Aluminum alloy is one of the most commonly used materials in CNC machining. However, there are many different grades, and the properties can vary significantly from one series to another. Common aluminum alloys are generally classified into the 1xxx through 7xxx series, as well as die-cast aluminum alloys.

1xxx Series: Commercially Pure Aluminum (1050 / 1060 / 1070 / 1100)

These grades contain more than 99.5% aluminum and are essentially considered commercially pure aluminum.

Characteristics: Very soft, easy to bend, form, and polish, with excellent electrical and thermal conductivity. However, because the material is so soft, it tends to stick to cutting tools during machining. Chip evacuation can also be difficult, and thin-walled parts are prone to deformation.

Typical applications: Heat sinks, electrical components, decorative panels, reflective parts, and products requiring a bright anodized finish.

Limitations: Very low strength, making it unsuitable for load-bearing applications.

2xxx Series: Aluminum-Copper Alloys / High-Strength Aluminum (2024 / 2017 / 2014)

Copper is the primary alloying element. After heat treatment, these alloys can achieve very high strength. They are widely used in aerospace applications and are often referred to as aerospace-grade aluminum.

Machining characteristics: The material has sufficient hardness for smooth cutting and produces clean, easily broken chips, with moderate tool wear. However, 2xxx-series aluminum has relatively poor corrosion resistance and may develop problems in humid environments.

Anodizing performance is also generally poor, so these alloys are not commonly selected when cosmetic anodizing is required. In addition, heat-treated material can contain significant internal residual stress. Stress relieving is recommended before finish machining; otherwise, the part may warp or distort.

Typical applications: Aircraft structural components, tooling and fixtures, high-strength mechanical parts, and defense-related components.

Limitations: Poor resistance to moisture and corrosion, with fewer suitable surface-finishing options.

3xxx Series: Aluminum-Manganese Alloys / Corrosion-Resistant Aluminum (3003 / 3004)

Manganese is the primary alloying element. These alloys have excellent corrosion resistance but cannot be strengthened through heat treatment.

Machining characteristics: The material is relatively ductile and can stick to cutting tools during machining, making chip evacuation less efficient. Strength is moderate to low, but corrosion resistance is excellent. Anodizing can also produce a uniform and attractive surface finish.

Typical applications: Water tank housings, outdoor equipment enclosures, sheet-metal parts, and pressure vessels.

4xxx Series: Aluminum-Silicon Alloys (4043 / 4032)

Silicon is the primary alloying element. These alloys are known for their low coefficient of thermal expansion and good wear resistance. The 4xxx series is mainly used for cast materials and welding applications, while extruded material is relatively uncommon.

Machining characteristics: Silicon particles are extremely hard and can cause significant cutting-tool wear. PCD diamond tools or cutting tools specifically designed for aluminum are often required.

4xxx-series extrusions are rarely used in CNC machining. In most cases, CNC machining is performed as a secondary finishing process on cast blanks.

Typical applications: Pistons, wear-resistant sliding components, and welding filler materials.

5xxx Series: Aluminum-Magnesium Alloys / Corrosion-Resistant Aluminum (5052 / 5083 / 5056 / 5754)

Magnesium is the primary alloying element. The 5xxx series offers some of the best corrosion resistance among aluminum alloys and cannot be strengthened by heat treatment.

Machining characteristics: These alloys are relatively tough and ductile, with a noticeable tendency to stick to cutting tools. Tool marks may also remain on the surface after finish machining.

However, the 5xxx series offers excellent weldability and very good anodizing results. 5083 provides higher strength than most other 5xxx-series alloys and is well suited for thick-plate structural components.

Typical applications: Equipment enclosures, electronic housings, marine components, solar mounting structures, and decorative components. For CNC-machined aluminum housings, 5052 is one of the most commonly selected materials.

6xxx Series: Aluminum-Magnesium-Silicon Alloys — The Workhorse of CNC Machining

The 6xxx series is the most widely used aluminum alloy family in CNC machining. Magnesium and silicon are the primary alloying elements. These alloys can be heat treated, such as to the T6 condition, and provide a good balance of strength, toughness, machinability, corrosion resistance, and cost.

6061 — The Most Commonly Used Aluminum Alloy

6061 offers excellent machinability, has relatively little tendency to stick to cutting tools, provides good dimensional stability, and makes tight tolerances easier to control. It also produces consistent results after anodizing.

It can be used for almost any general-purpose CNC-machined aluminum part.

Typical applications: Automation fixtures, module brackets, flanges, and various precision structural components. Unless there is a special material requirement, 6061 is usually a safe and cost-effective choice.

6063 — Primarily Used for Extruded Profiles

6063 is mainly used for extruded aluminum profiles. It is softer than 6061 and can be slightly more prone to sticking during machining, but it provides an excellent surface appearance after anodizing.

Typical applications: Aluminum frames, decorative trim, and machined components made from extruded profiles.

6063 is generally not the best choice for precision components that require heavy material removal.

6082 — A Higher-Strength 6xxx-Series Alloy

6082 contains relatively high levels of magnesium and silicon and provides higher strength than many other 6xxx-series alloys, along with good wear resistance and vibration resistance.

Typical applications: Heavy-duty structural components, construction and industrial machinery parts, and die or mold backing plates.

7xxx Series: Aluminum-Zinc-Magnesium-Copper Alloys / Ultra-High-Strength Aluminum (7075 / 7050 / 7068)

Zinc is the primary alloying element. After heat treatment to conditions such as T6 or T73, these alloys can achieve extremely high strength.

Machining characteristics: 7xxx-series aluminum is hard, cuts smoothly, and produces clean, well-broken chips. However, it generates more heat during machining, so sufficient coolant is essential.

These alloys may also contain significant internal residual stress. After rough machining, a stress-relief or stabilization process is often recommended before finish machining to reduce the risk of part distortion.

Corrosion resistance is not as good as that of 5xxx- or 6xxx-series aluminum. Anodized surfaces also tend to appear darker, so hard anodizing is commonly used for functional applications.

Typical applications: Aerospace components, drone structures, mold and die blocks, high-end fixtures, and racing components.

Limitations: High material cost and relatively poor corrosion resistance.

Die-Cast Aluminum Alloys — CNC Secondary Machining of Cast Parts

Common Grades: A380 (Approximately Equivalent to ADC10) / A383 (Approximately Equivalent to ADC12)

These alloys have relatively high silicon content. Components are first formed by die casting, while CNC machining is mainly used afterward for precision milling, drilling, tapping, and other secondary operations.

Machining challenges: Hard silicon particles accelerate cutting-tool wear. Die-cast blanks may also contain porosity, voids, and other casting defects.

Natural-color anodizing is generally unsuitable because the high silicon content and casting structure can produce an uneven or unattractive surface. Painting, powder coating, or other coating processes are therefore more commonly used.

Typical products: Motor housings, valve bodies, and die-cast components for small appliances.

Aluminum Grades for Special Applications

Quick Comparison of Common Aluminum Alloy Series

Material Selection Recommendations

• General precision fixtures and automation components → 6061-T6 — cost-effective and suitable for the widest range of applications.
• Equipment housings and cosmetic components → 5052
• High-strength load-bearing or aerospace components → 7075-T6
• Heat sinks and electrical components → 1060 / 1070
• Outdoor or marine environments → 5083
• Extruded aluminum frames and decorative profiles → 6063
• Secondary CNC machining of die-cast housings → A383