How to Choose the Right Aluminium Alloy Grade for Your Application

Selecting the right aluminium alloy grade is one of the most important decisions in the casting process. The wrong grade can lead to casting defects, poor mechanical performance, and costly production failures. This guide helps you understand which grade fits your application.

Understanding the Grading Systems

Aluminium alloy ingots are classified under different national and international standards. The most common systems used in India are:

• Indian Standard (IS) / BIS - Governed by the Bureau of Indian Standards.
• Japanese Industrial Standard (JIS) - Common in Japanese OEM supply chains operating in India (Toyota, Honda, Yamaha).
• British Standard (BS 1490) - Legacy standard still widely referenced, especially for LM-series alloys.
• American (ASTM/AA) - Used by some multinational manufacturers.

Different standards may describe similar compositions under different names. For example, ADC-12 (JIS), LM-2 (BS), and A383 (AA) are broadly similar alloys. Your procurement team should be able to cross-reference between standards.

Matching Grade to Application

For automotive die-casting (two-wheelers and four-wheelers):
ADC-12 is the default choice for most die-cast automotive components in India. It offers the best balance of castability, strength, and cost. If you are supplying to Maruti, Honda, Hyundai, or similar OEMs, ADC-12 is likely your starting point.

For components requiring higher strength:
LM-24 or ADC-10 offer improved mechanical properties. These are used where the component will bear structural loads or operate under higher stress conditions.

For corrosion-resistant applications:
LM-6 is the go-to choice. Its higher silicon content provides excellent fluidity and corrosion resistance. Used in marine environments, outdoor architectural applications, and electrical housings exposed to moisture.

For high-temperature applications:
AC4B and similar grades with controlled copper and silicon content provide good thermal stability. Used in engine blocks and components that operate at elevated temperatures.

For custom or niche applications:
Discuss your specific requirements with your supplier. A knowledgeable supplier can recommend or source custom compositions tailored to your exact casting process and end-use conditions.

Key Properties to Evaluate

• Castability - How well does the alloy flow into your mould? High silicon content (10-13%) generally improves fluidity. Critical for thin-walled or complex-geometry components.
• Mechanical Strength - Tensile strength and hardness matter for structural components. Copper additions increase strength but may reduce corrosion resistance.
• Machinability - Will the cast component need secondary machining? Some alloys machine more cleanly than others.
• Corrosion Resistance - Important for components exposed to weather, chemicals, or moisture. Silicon and magnesium improve corrosion resistance; copper reduces it.
• Thermal Conductivity - Relevant for heat sinks, engine components, and electrical applications where heat dissipation is critical.

Practical Tips for Buyers

Always request a test certificate with chemical composition data for each batch you receive. Compare against your required specification.

If you are switching grades or suppliers, run a trial batch through your production process before committing to full volumes. Even alloys within specification can behave differently in different die-casting setups.

Build a relationship with a supplier who understands your application. A good supplier does not just sell ingots - they help you solve production problems.