ALUMINIUM
Table of main properties of aluminium
| Property | Typical Value | Remarks |
|---|---|---|
| Density | ~2.7 g/cm³ | Low |
| Young’s modulus (E) | ~70 GPa | Low |
| Tensile strength | ~70–500 MPa | Depends on alloy |
| Hardness (HV) | ~20–150 HV | Low to moderate |
| Thermal conductivity | ~200–235 W/m·K | Very high |
| Electrical conductivity | ~30–38 MS/m | High |
| Thermal expansion | ~22–24 ×10⁻⁶ /K | Relatively high |
| Melting point | ~660 °C | Pure aluminum |
| Magnetism | No | Non-magnetic |
| Corrosion resistance | Good | Oxide layer |
| Machinability | Good |
- General description
- Types of aluminium used in watchmaking
- Surface treatments
- Watchmaking applications
- Advantages and limitations
Aluminum is a lightweight non-ferrous metal used in watchmaking for its low density, good machinability, and natural resistance to corrosion. Although its use has historically been more limited than that of brass or steel, it has gained increasing interest in contemporary watchmaking, particularly for components where weight reduction is required.
In its pure or alloyed form (aluminum with magnesium, silicon, or copper), it can meet specific requirements, especially in fast-moving components or structural elements where mass is a critical factor.
Main Properties
Aluminum alloys used in watchmaking exhibit several key characteristics:
- Low density (~2.7 g/cm³) → approximately three times lighter than steel
- Good corrosion resistance → due to the formation of a protective oxide layer
- Excellent machinability
- High thermal conductivity
- Non-magnetic properties
- Relatively low Young’s modulus (~70 GPa)
These properties make aluminum particularly suitable for components where inertia must be minimized.
1. Pure Aluminum
Used only marginally due to its low mechanical strength.
Characteristics:
- Very lightweight
- Easy to machine
- Low wear resistance
2. Aluminum Alloys
Alloys are preferred in watchmaking to improve mechanical performance.
Examples:
- Al-Si (aluminum-silicon) → good dimensional stability
- Al-Mg (aluminum-magnesium) → improved mechanical strength
- Al-Cu (duralumin type) → high strength
Applications:
- Lightweight components
- Specific structures
- Experimental or technical parts
Aluminum alloys are classified into different families depending on the principal alloying element. For wrought aluminum alloys, these categories are:
- Series 1000: Aluminum (>99%), unalloyed
- Series 2000: Main alloying element: copper (Cu)
- Series 3000: Main alloying element: manganese (Mn)
- Series 4000: Main alloying element: silicon (Si)
- Series 5000: Main alloying element: magnesium (Mg)
- Series 6000: Main alloying elements: magnesium (Mg) and silicon (Si)
- Series 7000: Main alloying element: zinc (Zn)
3. Anodized Aluminum
Anodizing is an electrochemical process that:
- Strengthens the surface
- Improves corrosion resistance
- Allows a wide range of colors
Applications:
Aluminum is often treated to enhance its performance:
- Anodizing → protection and coloration
- Vapor phase deposition (PVD, CVD) → coloration and wear resistance
- Polishing / microblasting → aesthetic finishing
Aluminum is used in a targeted manner:
- Lightweight movement components
- Experimental caliber structures
- Cases and external elements
- Tooling
Its low mass makes it particularly suitable for:
- Reducing inertia
- Improving shock resistance
- Optimizing energy efficiency