Magnesium and aluminum are die-castable alloys. Magnesium is lighter and goes well with the parts needing fuel efficiency and vibration damping. It needs certain handling techniques. Wherein aluminum is available at a cheaper price and fits general-purpose use. It resists corrosion well. Learn what unique properties of magnesium die casting and aluminum die casting differentiate them from each other. Also, discover their applications and fabrication considerations.

Properties of Magnesium and Aluminum

Magnesium Properties

Specific Alloys

Specific alloys of magnesium are basically formed through alloying methods. In which it is mixed with different elements. Examples include AZ91D, AM60, and AS41.

Better strength and improved ability to prevent corrosion are the significant properties of these alloys. For instance, AZ91D is stronger and lighter due to its 240 MPa tensile strength.

Corrosion Resistance

Magnesium can corrode because of what environments like air or alkaline solutions do. In that case, coating or alloying elements work best. For example, magnesium’s corrosion resistance becomes better when engineers mix it with aluminum.

Additionally, the lower density (1.74 g/cm³) in magnesium does not let it prevent corrosion well. So it needs certain protection.

Thermal Conductivity

Many magnesium alloys offer good thermal conductivity, like AZ91 (51 W/m-K). So, they conduct heat well but somehow not as efficiently as aluminum or copper does.

However, every time a metal is heated, it expands. That is known as thermal expansion. Magnesium offers greater thermal expansion at or near 25.2 x 10⁻⁶/°C than aluminum (23.6 x 10⁻⁶/°C).

Damping Capacity

Magnesium has an excellent vibration-damping attribute. That makes it well-suited for use in vehicles and airplanes. Because these parts need reduced noise and vibration, their elastic modulus is 45 GPa, referring to more flexibility. It is lower than aluminum (69 GPa).

Machinability

Magnesium alloys have a lower melting temperature (650°C) than Al. However, their machinability is weighed by various cutting forces, tool wear, and chip formation.

Its flammability, somehow, must be properly treated. This is because it can spark during machining.

Aluminum’s properties

Specific Alloys

A380, A383, and ADC1 are some kind of specific aluminum alloys. These alloys contain other elements like silicon, copper, and zinc.

That, therefore, gives better strength and corrosion resistance. For example, the 320 MPa tensile strength of the A380 makes it a better choice for industrial use.

Corrosion Resistance

The creation of a protective oxide layer in aluminum enables it to stand against corrosion in atmospheric and marine environments. Also, aluminum has a 2.70 g/cm³ density. That’s why it is stronger yet lightweight.

Electrical Conductivity

In aluminum alloys like A380, there is an electrical conductivity of 22.5% IACS (International Annealed Copper Standard). Basically, it is lower than copper but still works best for electrical wiring.

Castability

Aluminum alloys take on any complex shape because of their excellent castability. They smoothly flow into the mold and can create thin walls. That’s why it has become a popular manufacturing choice. Also, their high melting point lets them handle higher temperatures during casting.

Applications of Magnesium Die Casting

Aerospace

The lightweight and moderate strength of magnesium makes it usable for manufacturing several aerospace parts. That includes aircraft gearbox housings and helicopter rotor hubs.

Automotive

In the automotive sector, manufacturers use them because of their ability to use less fuel and being lightweight. The applications include instrument panels, steering wheels, tailgate inners, door panels, and steering hanger beams.

Electronics

Magnesium is also suitable for fabricating laptop cases and smartphone components. It reduces part weight and offers durability.

Weight Savings

Because magnesium does not contain more weight than aluminum, it can be used to make the steering wheel 40% lighter.

Speaking about the aerospace industry, it can save weight for gearbox housings instead of aluminum. This means planes work more efficiently.

Importance of Weight Reduction

As you have already discovered, the impact of lightweight features. However, applications like cars that use magnesium use less fuel and produce fewer emissions. Moreover, lighter planes fly far distances. Also, you can carry lightweight products more easily.

Applications of Aluminum Die Casting

Automotive

Aluminum is a metal that allows manufacturers to cast it in any shape and form. Its lightweight features and strength are suitable for making engine blocks, transmission housings, and wheels. As a result, applications use less energy and last longer.

Aerospace

It can handle high stress effectively. Therefore, aerospace companies use it for their structural components and electronic enclosures.

Industrial equipment

Aluminum alloys protect the parts from corrosion. Resisting it, they provide durability and wear resistance in those industrial parts, especially those that need it. For example, pumps and gearboxes.

Recyclability

Aluminum is recyclable. That’s how it is known for being a sustainable option. You can reuse its product material due to its never-ending chain. Also, it does not lose its quality and properties.

The process of aluminum recycling uses not more than 5% to extract primary aluminum from bauxite. That, therefore, reduces its environmental impact.

Benefits of Recycling Aluminum in Die Casting

Recycled aluminum is often used in die casting, too. Wherein it saves resources and costs. It is also an option to meet sustainable goals across various industries. Using recycled metal removes the carbon footprint and is suitable for making economic sense.

Manufacturing Considerations in Casting

Magnesium Casting

Die Temperature & Reaction

When the diecaster heats magnesium alloys at its melting point(650°C) it turns into molten form.

In order to handle this heated metal, pickingba die with lower temperatures is pointless. So, therefore a die must endure a minimum 700°C temperature. There are reactions caused when magnesium encounters oxygen. That can be oxidation or fire hazards.

To avoid this, you can choose between sealed furnaces, argon, or SF6 gas covers. Also, using dry tools helps stop oxidation.

Besides, considering proper shrinkage cavities and core placements reduces the chances of upcoming defects.

Die Material & Maintenance

The dies that are used to cast magnesium are commonly made with H13 steel (45-50 HRC hardness) and 4140 steel (28-32 HRC hardness).

H13 steel can endure around 600°C temperature. Somehow, it wears fast because magnesium creates reactions.

Adding draft angles helps in pushing out the cast part from the dies. That means it also aids in smooth die performance.

Additionally, the die goes longer because of what regular maintenance and nitriding coatings do.

Cycle Time

Magnesium casting solidifies faster. Each cycle takes no more than 20 to 40 seconds. Also, parting the line in dies lets it separate easily. That also saves production time.

Safety Measures

SF6 gas suppression aids in controlling those fire hazard situations that can happen during magnesium castings.

Additionally, avoid using water-based coolants. That’s because heated magnesium reacts violently with water.

The draft angles and parting lines do not create trouble during the process, reducing risk.

Surface Finishing

Adding 1 to 3-degree draft angles allows you to get better surfaces. Also, several post-casting coatings and paintings improve part appearance and protect them from corrosion.

Aluminum Casting

Die Temperature & Pressure

Aluminum casting needs stronger dies to operate at 350°C under pressures up to 140,000 kPa. This is because aluminum has high melting points, and higher pressure might cause cracking.

Die Material & Production Limits

Dies made with steel (H13) usually perform well and can complete 100,000 cycles before needing replacement.

The parting line here reduces stress and extends life. Furthermore, the optimization of die designs brings positive changes in durability and performance. These techniques also minimize costs associated with die replacement.

Cycle Time of Aluminum

Aluminum casting takes 20 seconds to 1.5 minutes to end each cycle. It creates parts with wall thickness around (2-10 mm).

Basically, its cycle time includes injection speed (1-5 m/s), die temperature (150-250°C), and solidification time (5-20 seconds). This is why this process is a bit slower but gives precision.

Safety Measures of Aluminum

Aluminum casting often emits fumes. So, it is important to work in ventilated areas. Also, wear heat-resistant PPE and maintain machine guards. There must be strict protocol associated with molten aluminum and die temperature. So you can prevent burns, fires, and inhalation hazards.

Surface Finishing of Aluminum

In the case of surface finishing, aluminum undergoes several processes. Wherein shot blasting, polishing, and anodizing go so well.

Aluminum casting produces parts with roughness (Ra) ranging from 0.8 to 3.2 µm.

Coatings like powder coating (60-120 µm thickness) therefore increase its durability and beauty. They reduce rust occurrence and improve its performance.

Comparison of Mechanical Properties

Magnesium and aluminum are two different metals possessing unique properties. This is why magnesium can be used for various manufacturing products. For example, manufacturers mix it with 43% aluminum to create alloys.

Similarly, 40% of magnesium is used for making structural metal. That’s how it highlights its importance in lightweight engineering.

Tensile Strength & Yield Strength

The tensile strength of metal shows its ability to handle forces before breaking.

Yield strength is the point at which a metal starts bending permanently.

Magnesium alloys like AZ91D, in particular, offer 240 MPa tensile strength and 150 MPa yield strength. That contributes to making it a lighter option for casting.

For what it’s worth in aluminum, there’s the advantage of its 320 MPa tensile strength  and yield strength up to 130 and 280 MPa in A380.

This is why these metals are used for high-stress parts.

Elongation & Impact Resistance

Metals can be stretched at certain limits before breaking, which refers to their elongation.

Elongation impacts metal resistance and demonstrates its ability to absorb shocks.

There is 5 to 6% elongation in magnesium and 4–8 J impact resistance. That’s what makes it more flexible and shock-absorbent.

However, in aluminum, the elongation range is 1 to 10% and has 3–5 J impact resistance. This means they are a little more brittle.

Fatigue Strength

Metals’ ability to resist repeated stress is what is known as fatigue strength.

Magnesium alloys give 70–150 MPa fatigue strength. Although they are less strong than aluminum, they provide reliability.

Fatigue strength in aluminum fluctuates between 90 and 180 MPa. So this makes it suitable for use in engine parts.

Hardness

The hardness of metals measures their scratch resistance. For example, magnesium has 60–80 HB hardness and is counted in the soft metals category. Meanwhile, aluminum is 70–100 HB harders. So it is more durable.

Creep Resistance

Heat impacts the quality and performance of the materials with the passage of time. The parameter creep resistance is a sort that measures metals’ heat resistance ability over time.

For example, magnesium is limited to high-heat use, so it weakens faster. In this case, aluminum is the alternative option because of its ability to face higher temperatures.

Conclusion:

In Magnesium die casting, alloys solidify quickly, but there are chances of higher fire risks. Meanwhile, aluminum takes a little bit more time to cool than magnesium. It, however, gives durability in manufacturing parts. You can use magnesium as a lightweight metal to produce large-volume parts quickly. On the other hand, aluminum suits stronger parts that must not corrode over time. However, the right selection of metal between magnesium and aluminum can be made by weighing application needs.