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Basic Knowledge - Article Series Part 1

Light Metal Alloys: Spotlight Aluminum

| Editor: Nicole Kareta

Aluminum is one of the most widely used alloys in the manufacturing of die cast parts. But what properties does this alloy have and in what applications is it used?

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Aluminum is a corrosion- and temperature-resistant, robust raw material.
Aluminum is a corrosion- and temperature-resistant, robust raw material.
(Source: gemeinfrei / Pexels)

The raw material aluminum is enjoying increasing popularity in processing industries worldwide. In 2017, the transportation industry and the construction sector were the front-runners in the use of aluminum, accounting for 26 % of global aluminum demand. The electrical engineering (14 %) and mechanical and plant engineering (10 %) sectors rank 2nd and 3rd respectively. At the same time, global demand for aluminum rose steadily from 46 million tons in 2012 to 59.2 million tons in 2017. Against this background, the following questions are becoming increasingly important for market participants: What is an aluminum alloy and what are the characteristics of aluminum alloys? The answers to this and an overview of the possible uses of aluminum alloys offer orientation in the market.1, 2

What are Aluminum Alloys?

Aluminum alloys are formed by combining aluminum with other metals, mainly manganese, magnesium, copper, silicon, nickel, zinc and beryllium. In most cases, Al99.5 (EN AW-1050A) is used as the base material. In this way, the strength values can be significantly increased, and other properties can also be positively influenced.

In the die casting sector, silicon is an essential element used to alloy aluminum because it improves castability. This is referred to as a eutectic alloy of aluminum and silicon. This aluminum-silicon alloy has excellent casting properties (thin liquid, low shrinkage) and high rigidity. It is generally easy to weld and corrosion resistant. The addition of magnesium and copper increases rigidity, while copper reduces corrosion resistance. Aluminum casting alloys with these elements are used as materials for engine and transmission housings in vehicle and aircraft construction, for instance.

The following classification applies to cast alloys, which is based on the European Standard (EN):

  • 1xx: Pure aluminum qualities
  • 2xx: Copper
  • 3xx: Silicon-Copper/Magnesium
  • 4xx: Silicon
  • 5xx: Magnesium
  • 7xx: Magnesium-zinc
  • 8xx: Pewter

What are the Characteristics of Aluminum Alloys?

Aluminum may be a good choice if a corrosion resistant alloy is sought that can withstand high temperatures (200 degrees Fahrenheit or more). While the contact of aluminum with extremely harsh conditions has always been an obvious corrosion risk, aluminum components last relatively long compared to other die cast alloys. If the outside of an aluminum component is damaged or corroded, the material can "heal" itself over time. Due to their robustness, aluminum products are therefore particularly suitable for very tough working environments.

Aluminum alloys have the following physical properties:

  • Electrical conductivity: Electrical conductivity depends both on the composition and on the heat treatment heat treatment condition. Electrical conductivity is used to check the heat treatment condition of some heat treatable alloys.
  • Thermal conductivity: The high thermal conductivity of aluminum alloys reduces the temperature load on components (wheels, pistons, cylinder heads). During welding, however, the high thermal conductivity also leads to problems (high energy density necessary, effects on residual welding stresses).
  • Density: The density of aluminum is about 1/3 of that of many other metals with the exception of titanium and magnesium. The density is only slightly changed by alloy formation. From the point of view of application technology, the weight base is less important than the volume base to compare materials. Based on the same weight, only magnesium has a larger usable metal volume than aluminum.

What are Aluminum Alloys used for?

Aluminum is widely used in the manufacture of housings for electronic components, lighting fixtures, marine hardware and antennas - and in many other applications. While the raw aluminum material may not be as appealing to the eye, the durability of the corrosion protection is superior, and it offers several different options when it comes to surface finishing including:

  • Anodizing
  • Painting
  • Powder Coating
  • Teflon coating
  • Electroplating
  • E-coating

As an alternative to high-strength steel, modern aluminum alloys offer ideal properties in terms of stiffness, rigidity and formability. These properties are of particular interest to the automotive industry, as they allow designing light, safe and sustainable vehicles.

Resource conservation and sustainability are becoming increasingly important in automotive engineering. In order to achieve these goals, optimized aerodynamics, reduced rolling resistance and innovative engine technology, but above all the weight reduction of the vehicles play a major role. Aluminum is therefore replacing common steel solutions in automotive production.

What Developments and further Areas of Application are suitable for Aluminum Alloys?

At the end of 2018, the American aluminum producer Alcoa presented a new NHT alloy. Manufacturers of shock absorbers, doors and other parts had problems with hot cracking during casting. This could be solved by further developing the aluminum alloy by improved castability.

The aerospace industry is also utilizing the lightweight design potential of aluminum. Bremen scientists are working on the optimization of a high-performance alloy that can also be used in space travel. In addition, a novel aluminum alloy is to be developed that has the same excellent material properties but is also more cost-effective. An interesting aspect is that these alloys are to be used primarily in additive production.

As aluminum alloys are increasingly used in additive production, modified aluminum and magnesium alloys must be developed in order to optimize rapid prototyping, for instance.

References

(1) Distribution of global aluminum consumption by main areas of use in 2016 and 2017, found in: https://de.statista.com/statistik/daten/studie/240721/umfrage/verteilung-des-weltweiten-aluminiumbedarfs-nach-sektoren/

(2) Worldwide demand for aluminum in the years from 2012 to 2017 (in 1,000 tons), found in: https://de.statista.com/statistik/daten/studie/156039/umfrage/weltweite-aluminiumnachfrage-seit-2006/

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