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MAXXALLOY – STRUCTURE®:

Die casting alloy for ductile, thin-walled structural parts

SAG Aluminium Lend GmbH + Co KG, Lend, Austria.

The manufacture of large structural parts with low wall thicknesses places considerable demands on the die casting alloy to be used. Besides having good fluidity and a low tendency to stick, the material must above all satisfy the conditions for optimum ductility.

High ductility in a cast component assumes the use of low-iron die casting alloys. The admixture of manganese has proven to reduce the tendency of the alloy to stick. Like iron, manganese reduces the tendency to stick in a die cast tool; however, the precipitations that form during hardening are noted for having a morphology that is more beneficial to the ductility.

In addition to manganese, specialist literature also refers to chromium and cobalt as suitable alloying elements[1] for reducing the tendency to stick. At the same time, high levels of these alloying elements can also lead to unwanted effects such as intermetallic precipitations in the heat retaining oven (in the form of oven slurry) or in the cast part[2]. The aim was to set an optimum composition that both achieves a low tendency to stick, and also  reliably avoids the formation of inclusions.

This knowledge led to the development of the die casting alloy SILAFONT® - 21, alloy type AlSi11MgMnCr. Setting the optimum Mn:Cr ratio to avoid intermetallic precipitations was a key aspect in developing the alloy. SILAFONT®  -21 has proven to be an outstandingly castable die casting alloy in the manufacture of die cast structural parts. In production use, the die cast alloy SILAFONT® - 21 has been noted for its virtually non-existent tendency to stick.

Experiences from the use of SILAFONT® - 21 in production encouraged the use of chromium in the naturally hard MAXXALLOY® materials. Another significant advantage of adding chromium to naturally hard aluminium-magnesium alloys is the increase in heat strength, which gives greater stability to the cast parts which are still hot during extrusion [3]. 

As part of a development project, the influences of the chromium admixture on a basic alloy of type AlMg5Si2Mn were investigated with regard to its mechanical properties. The chemical composition and achievable mechanical properties are shown in tables 1 and 2.

Si

Fe

Cu

Mn

Mg

Cr

Ti

Other

2.0 – 2.6

0.15

0.02

0.3 – 0.5

5.0 – 5.5

0.2 – 0.3

0.05-0.15

each 0.02

Table 1: Chemical composition of the investigated allow AlMg5Si2MnCr

Wall thickness

[mm]

0.2-limit
Rp 0,2 [N/mm²]

Tensile strength
Rm
[N/mm²]

Ductile yield
A 5
 [%]

Brinell hardness
HB 5/250

2 to 4

150 – 195

270 - 310

12 – 18

90 - 100

Table 2: Mechanical properties

The newly developed die casting alloy AlMg5Si2Mn is offered by SAG Aluminium Lend GmbH + Co KG under the brand name of MAXXALLOY – STRUCTURE®. Especially notable are properties such as favourable extrusion behaviour, reduced adhesion of the cast part when removing parts, as well as the outstanding mechanical properties.

The special property profile of the MAXXALLOY – STRUCTURE® die casting alloy is intended for use in the manufacture of thin-walled structural parts.

Contact:

SAG Aluminium Lend
GmbH & Co KG
A-5651 Lend 25
Tel.: +4364166500-233
Internet: www.sag.at

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