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Understanding Aluminum Alloys

Understanding Aluminum Alloys

One of the most important things to understand about using aluminum for part or product design purposes is that pure aluminum is only used in a limited way commercially. The majority of extrusions are made from aluminum alloyed with other elements. The most common elements used are magnesium (Mg), silicon (Si), manganese (Mn), zinc (Zn) and copper (Cu). Most aluminum extrusions are made from the following alloy series: 1000 series Al; 3000 series Al + Mn; 5000 series Al + Mg; 6000 series Al + Mg + Si; and 7000 series Al + Zn + Mg.

The 1000 series is non-heat-treatable and are often selected for products where high thermal and electrical conductivity are desired. They have low strength. The 3000 and 5000 series also are non-heat-treatable and are often used in drawn tubing for highly ductile applications and printer components. The 5000 series is mostly used in extremely corrosive environments such as marine. The 6000 and 7000 series are heat-treatable. They are the most commonly used extrusion alloys and have a wide range of applications.

Understanding Aluminum Alloys

6000 Series

For most extrusion applications, the 6000 series aluminum alloy is often the optimal choice. The 6000 series alloys are termed "soft alloys" because they are easy to weld and offer good resistance to corrosion, even in marine environments.

The 6000 series has good extrusion abilities and can be solution heat-treated during hot working at the extrusion temperature. Solution heat treatment enables some of the alloying elements, such as magnesium and silicon, to go into solid solution and can be maintained in a supersaturated state on quenching. This homogenous material is subsequently age hardened to obtain the required mechanical properties.

Among the 6000 series, the 6060 alloy offers low-to-medium strength and is easy to extrude even for complicated cross-sections. This material is well-suited for anodizing, both for decorative and protective purposes. It has good formability during bending in the T4 condition (i.e., the aluminum has been solution-quenched and naturally aged at 70F for 5-10 days before delivery to the customer). This material is highly suitable for anodizing, both for decorative and protective reasons.

The 6063 alloy has slightly higher strength than 6060, but is also marginally more difficult to extrude, especially if the cross-section is complicated.
Understanding Aluminum Alloys

Heatsink Application

Aluminum is considered an excellent choice for heatsinks because it absorbs heat better than other metals. In a recent case, Hydro Aluminum's metallurgical and extrusion design teams worked with a lighting fixture manufacturing company to extrude components for a heat sink, framework and connecting rails for a new model fixture.

The Hydro technicians teamed with the company's die vendors to develop a die to make the heatsink shape which required a difficult to extrude tongue ratio combined with a thin wall design. For the first test run, Hydro chose a standard 6063 aluminum alloy. Both the 6060 and 6063 alloys provide excellent extrusion ability and surface finish for lighting, windows and doors, marine, ventilation and consumer products.

During the first run with the 6063 billet, the tongues broke out of the die at high breakthrough pressures. To address these issues, Hydro drew on its experience in developing a new alloy recently that falls into the 6060 category. This new alloy improves manufacturability while delivering the same performance as other 6060 and 6063 alloys. It is well-suited for complex extrusions, allows for better surface finishes, and is a useful alternative to some 6063 solutions.

Hydro recommended switching to its 6060 alloy with the idea of tweaking it so that it could be extruded at lower breakthrough pressures, as this would give better overall extrudability and respond better to anodizing, which also happened to be the customer's finish option for this component.

With the go-ahead from the customer, Hydro ran a short run order of the tweaked 6060 alloy through its casthouse. While the 6060 alloy was being prepared, plant operations made a second die with a design modification to make it easier to extrude the heatsink tongues.

The first run through the press resulted in some of the fins being out of shape due to tongue defection and flow variance. Recognizing that this issue could be addressed before going into full production, the customer agreed to move forward with prototypes. Hydro was able to run the new 6060 alloy through the press with a lower breakthrough and faster speed.

Hydro operations employees then met with the customer to adjust the die design to eliminate the tongue deflection. The result was a new round of samples that proved successful.

Aluminum's Green Side

The choice of material is a critical decision in all product development designs. Sustainability issues related to material choices are becoming an increasingly important of the design process due to regulations in some industries as well as corporate initiatives to be more environmentally conscious.

Aluminum is an excellent choice when considering its environmental impact compared to other metals. All extrusion-based components produced by Hydro Aluminum in North America use primary-grade billet, which contains more than 70 percent recycled content (produced using Hydro's proprietary remelt technology). As a result, only 5 percent of the energy used in primary aluminum production is needed to remelt aluminum.

Understanding Aluminum Alloys
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