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Brass Die Casting vs Aluminum Die Casting: A Comparison of Two Popular Metal Casting Processes

Metal casting is a manufacturing process in which molten metal is poured into a mold cavity to produce metal parts and products. Two of the most commonly cast metals are brass and aluminum, due to their desirable properties and relative affordability. Brass and aluminum parts are often made using die casting, an efficient metal casting process ideal for complex, high-volume production.

While brass die casting and aluminum die casting utilize the same basic process, there are some key differences between casting these two non-ferrous alloys. In this article, we’ll compare brass die casting vs aluminum die casting and examine the advantages and ideal uses of each.

What is Die Casting?

Die casting is a metal casting process characterized by forcing molten metal under high pressure into a steel mold, called a die. The metal solidifies quickly in the die, allowing for the rapid production of complex, precise metal parts with a great surface finish right out of the mold.

Die casting is highly efficient compared to other casting methods. It has faster cycle times, high productivity rates, and minimal material waste. Die casting also enables complex geometries, thin walls, and close tolerances unachievable with other mass production techniques.

Brass Die Casting

Brass is an alloy composed primarily of copper and zinc, along with small amounts of other elements like lead and aluminum. The exact brass composition can be adjusted to create alloys with specific material properties.

Brass is valued for its strength, corrosion resistance, machinability, acoustic properties, and attractive gold-like appearance. It has traditionally been used for musical instruments, valves, and fittings. Brass die casting is ideal for producing these and other precision brass components and parts at high volumes.

Benefits of brass die casting:

- Excellent dimensional consistency and tolerance control
- Ability to cast complex shapes with fine details
- Smooth, burr-free, high quality surface finishes
- High production rates and low unit costs for large volumes
- Suitable for small, thin-walled, and fragile casting designs
- Less porous than sand casting or permanent mold casting

Brass die cast parts require minimal post-processing - only basic trimming and surface finishing. Brass also plates and polishes well for an attractive decorative appearance.

Common applications of brass die casting include:

- Automotive parts like locks, knobs, and fittings
- Plumbing system components like valves, pumps, and couplings
- Musical instruments
- Small consumer product parts like buckles, zippers, buttons
- Electrical components like terminals, connectors, relay housings
- Decorative hardware and fixtures

Aluminum Die Casting

Aluminum is a lightweight, ductile, and easily cast metal. Pure aluminum has relatively low strength, but when alloyed with elements like silicon, magnesium, and zinc, aluminum alloys boast high strength for their low density.

Aluminum and its alloys have high thermal and electrical conductivity and excellent corrosion resistance. Aluminum die casting allows these beneficial properties to be put to use in high-volume, precision components and products.

Benefits of aluminum die casting:

- Light weight compared to zinc, iron, and steel alloys
- Ability to produce thin-wall castings down to 1 mm thickness
- Excellent castability for intricate, detailed casting designs
- High productivity and quick cycle times support large production runs
- Consistent dimensional accuracy and mechanical properties
- Heat and corrosion resistant aluminum alloys available

Common applications of aluminum die casting include:

- Automotive parts like housings, pistons, car wheels
- Aerospace and defense components
- Consumer electronics housings and frames
- Appliance parts like air conditioner coils and motor housings
- Medical equipment components
- Recreation products like ski poles, baseball bats, golf club heads
- Furniture fittings and hardware

Comparing Brass vs Aluminum Die Cast Parts

Brass and aluminum are both commonly die cast metals, but there are some key differences between the two. Some of the main comparisons are:

Density - Brass is denser than aluminum. Brass has a density around 8.5 g/cm3 while aluminum's density is approximately 2.7 g/cm3. Aluminum die castings will be lighter.

Melting point - The melting point of brass alloys ranges from 900-1000°C. The melting point of die casting aluminum alloys is much lower, between 580-660°C. More energy is required to melt and cast brass.

Strength - Many aluminum alloys offer higher tensile and yield strength than common brass alloys like yellow brass. Heat treatable aluminum alloys can achieve tensile strength above 45,000 psi.

Castability - Brass has better castability than aluminum, allowing it to more precisely replicate mold details. Aluminum's faster freezing can lead to less intricate as-cast surfaces.

Corrosion resistance - Brass provides excellent corrosion resistance in a wide range of environments. Some aluminum alloys have poor corrosion resistance and may need protective coatings.

Machinability - Brass is extremely easy to machine into final products compared to aluminum and its alloys.

Appearance - Brass has a distinctive gold-like sheen, while aluminum has a grayish, metallic appearance. Aluminum can be anodized or painted for color.

Cost - Brass alloy is generally more expensive than aluminum alloy. Aluminum benefits from lower raw material costs.

When selecting between brass vs aluminum for a die casting application, factors like required strength properties, product weight, complexity of the casting geometry, machining needs, and cost will help determine the best material choice.

Design Considerations for Brass and Aluminum Die Cast Parts

Die casting produces complex, high-quality metal components suitable for demanding industrial applications. But designing parts specifically for die casting is vital to achieving desired results. Here are some key design considerations for brass and aluminum die cast parts:

- Add draft angles and fillets/radii to avoid areas prone to cracking and improve mold flow.
- Include multiple gates/ports spaced around the part to ensure complete mold filling.
- Uniform wall thickness and cross-sections will prevent defects like sinks and porosity.
- Include steel support inserts for attachments like threads and hinges.
- Limit undercuts and re-entrant angles that would lock the part in the die.
- Brass parts should have minimum wall thickness around 0.020 inches.
- Minimum recommended wall thickness for aluminum is 0.060 inches.
- Detailed projections and fine features may not fill completely for aluminum due to rapid solidification.

Secondary Operations for Die Cast Parts

While die casting produces complete, net-shape parts, some additional fabrication operations help prepare components for end-use:

- Trimming and cutoff to remove extra material like sprues and flash.
- Drilling and tapping to add holes for fasteners and attachments.
- Surface finishing like sanding and polishing to improve appearance.
- Plating or coating for enhanced corrosion and wear resistance.
- Joining processes like welding and adhesive bonding to assemble subcomponents.
- Machining and CNC operations to achieve critical dimensions and tolerances.

By utilizing secondary finishing procedures, mechanically robust, aesthetically pleasing die cast brass and aluminum components can be manufactured to meet product performance requirements.


Brass and aluminum are two versatile alloys commonly used in die casting. Both enable economical production of complex, high-quality metal parts suitable for a wide range of industries.

Factors like part strength, weight, material properties, machinability, appearance and casting characteristics help determine which alloy is optimal for a given application. With careful design and secondary finishing, brass and aluminum die castings can provide exceptional functionality, precision, and service life for metal components and products. CNC Milling CNC Machining