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THE MAGNESIUM ADVANTAGE

At 1.8g/cm3, Magnesium is the lightest of all structural materials and 100% recyclable. It delivers:

  • The best strength-to-weight ratio of any commonly used structural metal.
  • Excellent dimensional stability as well as high impact and dent resistance.
  • Exceptional dampening capacity and low inertia making it ideally suited for parts that undergo frequent and sudden changes in motion direction.
  • The newer high purity alloys can deliver better corrosion resistance than Carbon, Steel and most Aluminium alloys.

 

Other key advantages include:

  • Thin-walled die-casting means structures can be made as one piece rather than assembled from several components. This simplifies design, lowers assembly costs, improves reliability, minimizes tooling costs and reduces joints, fasteners and welds.
  • Consistent and predictable shrink rates mean minimal distortion or casting stress.
  • Low heat content means less energy is required to reach casting temperatures and castings cool quicker so cycle times are faster.
  • Lower temperatures and low affinity for iron reduce the effects of thermal fatigue and erosion on dies so they last longer.
 

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MAGNESIUM VS ALUMINIUM

Imagine a car made entirely of die-cast Aluminium parts. Now imagine that exact same car made from die-cast Magnesium parts. The Magnesium car would be 1/3 lighter in weight than its Aluminium cousin. The Magnesium die-cast parts outperform the Aluminium ones in many ways. The advantages include:

  • 33% lighter than Aluminium.
  • Similar or greater mechanical properties.
  • Lower working temperatures extend die life and reduce energy consumption during production.
  • Machining is faster and easier and machining tools last significantly longer.
  • Superior thin-walled near net shape casting of larger, more complex parts so there are fewer components and less assembly required.
  • Greater general corrosion resistance.
 
MAGNESIUM VS STEEL

As standards for greater fuel economy tighten and automobile designs become more complex, Steel simply can't deliver on higher performance expectations. Magnesium requires far less energy during the entire die-cast production process and designs can be far more elaborate without sacrificing strength. Tolerances are tighter and the fit and finish of the final product is vastly superior. The advantages Magnesium offers over Steel include:

  • 75% lighter than Steel.
  • Complicated thin-walled near net shape casting that would be impossible to achieve using steel.
  • Consolidation of individual components into a single die-cast Magnesium part, which improves rigidity while reducing welding costs and assembly time associated with Steel.
  • Tooling costs are significantly reduced due to consolidation of multiple parts into a single part.
  • Lower working temperature reduces energy consumption during production and extends die life.
  • Superior dimensional stability and repeatability.
 

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mgplastic

MAGNESIUM VS PLASTIC

Upon superficial examination, Plastic can appear quite appealing, primarily because of the reduction in weight and the initial cost comparison. Upon closer inspection, however, those advantages can quickly evaporate. Compared to die-cast Magnesium parts, Plastic parts are often subject to dimensional stability issues, surface deterioration, fit issues due to temperature changes and a lack of rigidity. Die-cast Magnesium parts typically outperform plastics by delivering:

  • Stronger and greater wear resistance than Plastic.
  • Superior stiffness as Plastic often requires significant reinforcing.
  • Greater impact resistance and energy absorbing capacity.
  • Superior thin-walled near net shape casting of larger parts.
  • Higher temperature applications.
 
CAFE STANDARDS

Going farther, using less

Corporate Average Fuel Economy (CAFE) Standards were introduced in 1978 to reduce energy consumption by increasing fuel economy. The Standards have increased steadily over the years since then, pushing auto-makers to improve fuel efficiency in new and innovative ways. In May of 2012, CAFE Standards were tightened yet again. By 2017, the CAFE Standard will be 35.5 mpg and 54.5 mpg by 2025.

 

Magnesium meets the challenge

Increasingly, automobile manufacturers worldwide are turning to lightweight Magnesium and Magnesium alloy parts as a way to reduce overall vehicle weight and improve fuel economy.

 
LIGHTWEIGHT ALLOYS

The vast majority of Magnesium die-cast automobile parts are made from three different Magnesium alloys. Each is formulated to achieve a unique set of properties and performance characteristics best suited to specific applications. They are:

AZ91D

Most commonly used alloy for high pressure die-casting. Offers excellent strength-to-weight ratio, very good corrosion resistance and superior castability. This alloy is typically used for powertrain and mechanical components where toughness is more important than deformation capability.

AM60B

Commonly used for die-casting automotive safety components such as instrument panel structures and seat frames. This alloy offers excellent ductility, energy absorbing properties, strength and castability.

AM50A

With a lower Aluminium content than AM60B this alloy offers a further increase in ductility but at a slightly reduced strength and a slight reduction in castability. It is typically used where the performance requirements demand elongation properties beyond that of AM60B.

Mechanical Properties AZ91D AM50A AM60B
Ultimate Tensile Strength (Mpa) 240 210 225
Yield Strength (Mpa) 160 125 130
Elongation % ub 2 in (51mm) 3 10 8
Hardness (Brinell) 70 60 65
Elastic Modulus (Gpa) 45 45 45
Charpy Impact (unnotched) (J) 6 18 17

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Specialty alloys for specific applications

For applications such as power-train components where the operating temperature is above 120°C, such as automatic transmission housings, there are a number of Magnesium alloys available. These alloys are designed to operate in the higher temperatures without "creep" so that bolt tension and sealing surface flatness is maintained. 

Physical Properties AZ91D AM50A AM60B
Density (g/cm3) 1.81 1.77 1.80
Melting Range (°F) 815-1108 815-1138 815-1139
Melting Range (°C) 435-598 415-620 435-615
Specific Heat (kJ/kg k) 1.02 1.02 1.02
Coefficient of Thermal Expansion (um/m-k) 26.0 26.0 26.0
Thermal Conductivity (W/m-k) 51 65 61
Thermal Conductivity (W/m-k) 51 65 61
Electrical Conductivity (MS/m) 6.60 9.10 nm
Corrosion Rate (mg/cm2/day) 0.05 0.10 0.09
 
MAGNESIUM DIE-CASTING FAQ

The benefits of using Magnesium components in today's automobiles are compelling. It's 75% lighter than Steel, 33% lighter than Aluminium, offers component and feature integration and provides a high dimensional stability that improves fit and finish.

  • About Magnesium
  • Magnesium is the lightest of all structural metals - about 33% lighter than Aluminium, 75% lighter than Steel - it is non-toxic, non-magnetic, it has high-impact strength qualities and its resistant to denting. These characteristics make Magnesium incredibly useful for a wide range of applications, with the auto and aviation industries being prime examples.  Magnesium is also now used extensively in the manufacture of consumer electronics and tools, sporting equipment, medical devices and batteries. Magnesium powders and raspings are also widely used in the steel industry as a desulfurization agent and the chemical industry.

    Magnesium when alloyed with small amounts of Al, Mn, Si and Zn yields alloys with excellent properties and high ratios of strength-to-weight. Proper combinations of these alloying constituents provide alloys suitable for sand, permanent mold and die-castings, forgings, extrusions, rolled sheet and plate. Shemaco produces and supplies a complete range of die-casting, sand-casting and wrought alloys. 

  • Magnesium Mechanical Properties
  • Magnesium Manufacturing Processes
  • Magnesium Casting

    Magnesium castings characterized by good surface appearance and high-strength-to-weight ratio can be obtained in a wide variety of intricate shapes. Sand, permanent mold and die-casting are the methods most commonly used to produce cast structures. The selection of a proper alloy for a particular use depends upon the service requirements of the job as well as relative properties and characteristics of the casting alloy. The most common casting alloys are AZ91B, AM50A and AM60B. AZ91D is the most common alloy used in high pressure die-casting, as it offers good strength-to-weight ratio and excellent castability. AM50A and AM60B are used for safety components in the automotive industry given their superior ductility and energy absorbing properties combined with good strength and castability. AM20 is another Mg-Al alloy used for special safety components that offers high ductility and impact strengths.

     

    Die-casting of Mg parts

    Most Magnesium automotive parts are made by die-casting. Magnesium die-casting has several advantages over Aluminium:

    • Most molten alloys show high fluidity which allows casting of intricate and thin walled parts. Magnesium may be used for casings with thinner walls (1–1.5 mm) than is possible with Aluminium (2–2.5 mm) or Plastics (2–3 mm).
    • Magnesium has a latent heat of fusion per unit volume that is 2/3 lower than that of Aluminium. This means that Magnesium castings cool more quickly and die wear is reduced.
    • High gate pressures can be achieved at moderate pressures because of the low density of Magnesium.
    • Iron from the dies has very low solubility in Magnesium alloys, which is beneficial because it reduces any tendency to die soldering.
      
     

    Magnesium Extrusions

    Magnesium alloys are readily extruded into an almost unlimited variety of round rods, bars, tubes and structural shapes. The process for extruding Magnesium is almost the same as the process for extruding Aluminium materials. Most common is direct extrusion without a lubricant. Cylindrical ingots are heated to 300-400°C and pressed through dies.

    With some of the alloys it is possible to extrude Magnesium on the standard dies that are normally used for Aluminium extrusions with a small correction to the die. As a result, there is a wide range of standard profiles that can be extruded without big investments in new dies. The second added value for the customer is that for new designed profiles, one only needs to invest in a single die for extruding profiles in Aluminium and Magnesium. Generally extrusion speed for Magnesium is much slower than for Aluminium.

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