Cast Aluminium Alloys for Automotive Components: Why OEMs Are Shifting to Recycled ADC12/LM Grades

Walk into any modern automotive die-casting facility and you'll find components - transmission housings, engine brackets, structural parts - cast almost entirely from secondary (recycled) aluminium alloys, not primary metal. This isn't a compromise OEMs and Tier-1 suppliers are making reluctantly. It's a deliberate shift, driven by cost economics, supply security, and sustainability targets that increasingly shape automotive procurement decisions.

A significant part of the secondary aluminium industry is built around producing cast alloys from recycled aluminium scrap. The use of recycled feedstock can support resource efficiency while allowing manufacturers to produce alloys to defined chemical and quality specifications. 

 This guide explains why these grades dominate automotive casting, what's driving the move to recycled material specifically, and what OEMs and component manufacturers should know when sourcing.

Why Cast Alloys, Not Wrought Alloys, Dominate Automotive Components

Automotive aluminium use splits broadly into two categories: wrought alloys (sheet and extrusions, used for body panels and structural extrusions) and cast alloys (used for complex, near-net-shape components produced via die casting, sand casting, or gravity casting). Engine blocks, transmission housings, brackets, pump bodies, and structural castings fall into the cast category - Al-Si alloys, including grades such as ADC12 and LM-series alloys, are widely used for cast components because of their casting characteristics and suitability for a range of applications.

The reason comes down to casting behaviour. Al-Si alloys have excellent fluidity in the molten state, allowing them to fill complex die cavities completely before solidifying - critical for producing thin-walled, intricate automotive components without defects. They also offer good pressure tightness, dimensional stability, and machinability once cast, which is why they've become the standard for high-volume die-cast automotive parts.

Understanding the Key Grades: ADC12, LM6, and LM24

ADC12 is the widely used die-casting alloy in the automotive industry, particularly across Asian manufacturing supply chains. It offers excellent fluidity and pressure tightness, making it the default choice for complex, thin-walled components like transmission cases and engine covers.

LM6 is known for strong corrosion resistance and is commonly used where components face exposure to moisture or marine-type environments - relevant for certain underbody and exposed automotive parts.

LM24 offers a strong balance of machinability and mechanical strength, often selected for components requiring post-casting machining operations.

Each grade is essentially a specific ratio of silicon, along with controlled additions of copper, iron, and other elements, engineered for a defined performance profile. For a deeper look at how these ratios are controlled during manufacturing, see our guide on what an aluminium alloy ingot is and how it's manufactured.

The Role of Recycled Aluminium in Cast Alloy Production

Aluminium recycling provides a way to recover aluminium from industrial and post-consumer scrap and return it to manufacturing. For alloy producers, the challenge is to process and segregate scrap appropriately and control the resulting chemical composition so that the finished alloy meets the required specification.

Gravita sources aluminium scrap from domestic and overseas markets and maintains segregation and collection controls to support the required raw-material quality. Its aluminium alloys are produced with process monitoring and batch-level checks, with products manufactured to customer specifications.

The Business Case Driving OEM Adoption

Energy and cost efficiency. Producing aluminium from recycled scrap requires roughly 5-10% of the energy needed to produce primary aluminium from bauxite ore, since it skips the energy-intensive electrolytic reduction process entirely. This translates directly into a cost advantage for recycled cast alloys compared to primary-grade material, at comparable performance for cast component applications.

Supply security. A well-developed secondary aluminium supply chain can provide manufacturers with access to recovered material from multiple sources. Consistent segregation, quality control and procurement capability are therefore important when supplying cast alloy manufacturers.

Sustainability and ESG reporting. As OEMs face increasing scrutiny on supply chain emissions (Scope 3, in particular), the significantly lower carbon footprint of recycled aluminium versus primary aluminium is becoming a quantifiable line item in supplier scorecards, not just a marketing claim.

No performance trade-off for the application. Recycled aluminium is not automatically lower quality than primary aluminium. For cast alloy applications, performance depends on factors such as chemical composition, cleanliness, process control and whether the material meets the required alloy specification. Consistent refining, filtration and quality testing are therefore critical to producing casting-ready alloys.

For a broader look at how recycled aluminium sourcing helps manufacturers control raw material costs more generally, see our guide on aluminium scrap recycling in India: how manufacturers can cut raw material costs.

What OEMs and Casting Units Should Check When Sourcing

Consistent chemical composition batch-to-batch. Since cast component tolerances depend on predictable alloy behaviour during die filling and solidification, variability in silicon, iron, or copper content between ingot batches can affect casting yield and defect rates. Ask suppliers for composition certificates per batch, not just a nominal spec sheet.

Degassing and inclusion control. Molten metal quality - particularly hydrogen content and non-metallic inclusions - directly affects porosity in the final cast component. Manufacturers using proper degassing and filtration in ingot production (rather than basic remelting) produce more casting-ready material.

Traceable scrap sourcing. For OEMs tracking recycled content for ESG or customer disclosure purposes, working with a manufacturer that can document scrap sourcing and recycled content percentage supports downstream reporting requirements.

Scalable supply. High-volume automotive production needs a supplier who can deliver consistent tonnage on a recurring schedule, not just spot-lot availability - particularly important for Tier-1 suppliers running continuous casting lines.

Why Automotive Manufacturers Work With Gravita

The consistency of an aluminium alloy depends not only on the nominal grade but also on raw-material selection, segregation, refining, alloying and process control. Buyers should therefore consider a supplier's ability to maintain consistent specifications across batches and meet the requirements of their casting process. 

Gravita India manufactures a full range of aluminium alloy ingots, including ADC12, LM6, LM24, and custom AlSi, AlMg, and AlCu formulations, from an integrated recycling and refining operation. With controlled melting, degassing, and filtration processes, and a scrap procurement network built for consistent, traceable sourcing, Gravita supplies casting units and automotive component manufacturers with the batch consistency that high-volume die-casting operations require.

The company's aluminium recycling operations source scrap from domestic and overseas markets, with segregation and collection controls designed to support raw-material quality. 

Frequently Asked Questions

Is ADC12 always a recycled alloy, or can it be made from primary aluminium? 

ADC12 and similar die-casting alloys can technically be produced from primary aluminium, but they are conventionally and predominantly manufactured from recycled aluminium scrap, since the alloy's composition aligns naturally with what recycled feedstock provides - this has been standard industry practice for decades, not a recent shift.

Does using recycled aluminium alloy reduce the mechanical performance of cast automotive components? 

Not necessarily. For cast components, the alloy is engineered around the properties recycled feedstock provides, and performance (fluidity, pressure tightness, machinability) is a function of the alloy's chemical composition, not whether the source metal was primary or recycled.

Why is recycled aluminium becoming more important to manufacturers? 

Aluminium recycling helps reduce dependence on virgin raw materials and supports more circular manufacturing. As companies place greater emphasis on resource efficiency and supply-chain sustainability, the quality, consistency and traceability of recycled aluminium feedstock are becoming increasingly important. 

What's the difference between ADC12, LM6, and LM24 for automotive use? 

ADC12, LM6 and LM24 are different aluminium alloy grades with different chemical compositions and property profiles. The appropriate grade depends on the casting process, component design and required performance. Buyers should select the alloy against the applicable specification rather than choosing a grade solely based on its general application.

Sourcing ADC12, LM6, LM24, or custom aluminium alloy ingots for automotive casting? Connect with Gravita's aluminium alloys team for specifications and pricing.