The principles of hardening in Aluminium Alloys can be described as follows:
a. Aluminium alloys with a total of up to 1% alloying elements consisting of Silicon, Manganese and Zinc iron in accordance with the desired properties, the maximum tensile strength can be achieved through the forging process (Forging) or various methods of cold working and the level of ductility can be obtained by increasing the number or type of alloy material even if it is relatively expensive.
b. Aluminium alloys with a total alloying elements up to 2.4% including 1.2% Manganese.
c. Aluminum alloys with various alloying elements as well as varying levels up to above 7% according to the needs.
Various types of aluminum alloy as mentioned is a solid solution structure with a little two-phase solution. Equilibrium diagram (Figure 1.14) are shown in the following is a form of balance for Aluminum-Magnesium alloy which this diagram shows that the element magnesium dissolves in the aluminum increased with increasing heating temperature.
This alloy is not a major problem because through the process of this alloy will only increase the voltage slightly but evenly. The structure of the solid solution (Solid Solution) is characterized by a soft but highly resistant to corrosion.
Aluminium alloys capable of heat treatment
Nature capable of heat treatment on the aluminum alloy material will provide the opportunity to be given an increase in voltage through the heat treatment process. On the principles of heat treatment can be seen in the chapter on Heat Treatment Control of mechanical properties of metal through the heat treatment process.
The process of heat treatment on aluminum alloys can be considered as:
Alloying element in aluminum with a copper content of up to 4% with a mixture CuAl2 hardening alloys with the medium.
Alloying element in aluminum alloys with a total of up to 2% above the etrdiri Silicon and Magnesium, MG2Si a hardening medium. Variations on Aluminum alloy elements consisting of Copper, Silocon as hardening media.
Heatreatable nature (able to heat treatment) of the aluminum alloys fall into two groups, namely the hardening solution spontaneously after formation, while others require advanced process, the heat treatment process known as “precipitation treatment” with the aim to improve nature.
In this process required a variety of additional elements such as elements that are increasing the hardness, tension, such as iron and zinc. If this Aluminum Alloy will be used at high temperatures it is necessary element Nickel.
• Cast Aluminum Alloys
If necessary Aluminum Alloy with properties of high ductility and corrosion resistance properties are also high on the commercial purity aluminum which has the added element-unsuar Silicon and Magnesium, thus also be obtained Aluminum alloy is hard and strong with a complex blend.
Based on the equilibrium diagram (Gambar1.15) where we need the following circumstances are very liquid alloys with Silicon levels greater than 5%, and is therefore based on the diagram that mengindikasikanterjadinya Eutectic compositions are at a level of 11.6% Silicon, Aluminum alloy thus This match is formed through the sand mold casting, die casting Grafity, pressure die casting with cold chamber die casting. Aluminum alloys of this group belong to the Aluminum alloys capable of heat treatment to increase strength and voltage.
Part of the equilibrium diagram Aluminum-Silicon Alloys
• “As-Cast” Aluminum Alloys
There are three main groups of “As-Cast” Aluminum Alloys are:
1) Aluminum alloy with levels of 9% to 13% Silicon,
Aluminum alloys can be formed by casting Die-Casting method.
2) Aluminum alloy with a composition consisting of 1.6% Copper and 10% Silicon can be formed by pouring through pressure die casting method.
3) Aluminum Alloy with 4.5% magnesium levels; and 0.5% Manganese, although this alloy has only medium voltage but has good corrosion resistance properties.
4) Aluminum alloy can be formed through the process of molding foundry sand (Sand-Casting) and Grafity Die Casting.
5. Properties capable of heating on Cast Aluminum alloy
With the addition of alloying elements such as elements of Silicon Aluminium Alloys and various other elements is sufficient to provide hardening function. The largest number of alloy materials in Aluminum Alloys obtained from elemental copper (Cu) with levels of up to 4% is added to the element Nickel slightly to 3% which will result in a mixed media hardening of Al 3 Ni.
• Heat Treatment on Aluminium alloy
Increased tension with heat treatment Aluminum Alloys having a composition corresponding to increased strength, heat treatment of this material will melt followed by the deposition process (precipitation). For this state the material response to warming the reaction will be characterized by the limits of solid solution (solid solution) in the solution until it reaches room temperature which increases according to changes in temperature itself.
Behaviour of Copper and Aluminium way pemaduannya the balance can be illustrated in the diagram (Figure 1.16) follows.
With only 0.2% Copper at ALuminium will produce a mix between Al2 Cu.
Aluminum-Copper
Solid solution (Solid Solution) of Copper on Aluminum The temperature increases with the increase reaching a maximum temperature of up to 5.7% at 584%, but if the content of the element Copper is less than 5.7%, then all will go into solid solution (solid solution) , when given sufficient heating to a high temperature.
If the alloy has to be in balance through a cooling process, for example after pouring, the advantages of copper will gradually precipitate from solid solution in the form of a mixture of a very hard and brittle Cu Al2 that collects in the grain boundaries.