ALLUMINIUM CASTING ALLOYS Essay Example

Aluminum Casting Alloys

Overview

Aluminum casting alloys are those metallic mixtures which have aluminum as their predominant components. Typically, the most commonly utilized alloying elements include magnesium, copper, manganese, zinc, and silicon. Casting alloys constitute one of the two main categories of aluminum alloys commonly found in the market today. The other category is referred to as the wrought alloys. Casting alloys are further subdivided into non-heat-treated and heat treated subcategories. Although 85% of all aluminum is utilized for the manufacture of wrought products, the usefulness of casting alloys can never be underestimated (Zolotorevskii & Belov, 2007).

Cast alloys of aluminum facilitate the yielding of products cost-effectively. This is mainly because aluminum has a lower melting point as compared with most other metals. Among the main weaknesses of cast aluminum is that it has a low tensile strength. Nevertheless, this cannot deter its use since it is cheap and has several other benefits. Among the most valued cast aluminum alloys id the Al-Si. In this alloy, significant levels of silicon are utilized. The high levels contribute towards remarkable casting characteristic features (Warmuzek, 2004).

Cast aluminum alloys are being widely utilized in the construction of engineering components and structures. They are mostly utilized in cases where light weights and corrosion resistance is of essence. For instance, cast aluminum alloys have been found to be useful components in the manufacture of aerospace. Their use began as soon as the manufacture of metal skinned airplanes commenced. Alloys of aluminum-magnesium have been found to posses two important qualities: they are lighter as compared to other alloys of aluminum, and they are also less flammable as compared to other alloys which contain high percentages of magnesium (Zolotorevskii & Belov, 2007).

Cast aluminum alloys retain their shiny nature even in dry conditions. This happens since there is always the formation of clear protective layers of aluminum oxides. During wet conditions, the alloy adapts what is referred to as the galvanic corrosion. This usually happens when aluminum alloys are placed in electrical contacts together with metals possessing negative corrosion capacities than aluminum. The compositions of alloys of aluminum are registered with an organization referred to as The Aluminum Association. Several organizations have been publishing more specified standards of aluminum alloys. The organizations include the Society of Automotive Engineers and other standardized subgroups (Warmuzek, 2004).

Raw Materials and Extraction

Aluminum is an abundant metallic element that is never found pure. Commonly, it is found in form of aluminum silicate, or while mixed with such other metals as iron, calcium, iron, and magnesium. The silicates are usually not useful ores since they are chemically difficult. This means that the manufacturers or smelters have to undertake an expensive process where pure aluminum is extracted. Bauxite is an impure aluminum oxide which is also hydrated. This compound is the main source of pure aluminum as well as several of its compounds (Persson, 2011).

Aluminum was discovered almost simultaneously by Paul L.T. Heroult and Hall, M.C. The two discovered the aluminum oxide especially because it could dissolve in fused cryolite. Aluminum is then decomposed through electronic means in order to attain the crude metal while molten. This technique is considered to e relatively cheaper than the extraction of other metals. Nonetheless, there are other methods of extracting aluminum and its compounds from the raw materials. The enhanced extraction is meant to improve the quality of the extracts. Currently, smelters have been able to achieve 99.5% quality, and they are still endeavoring to achieve 99.99% (Warmuzek, 2004).

Characteristics of Cast Aluminum Alloys

Cast aluminum alloys possess wide range of characteristic properties. This is why they have been considered to be essential in the construction of engineering structures. All the alloys have been classified using a number system which is referred to as ANSI. Most of the other classifications are accomplished according to the main alloying components (Persson, 2011).

The selection of the most appropriate cast aluminum alloys for a certain application involve the consideration of the alloys density, ductility, tensile strength, workability, formability, corrosion resistance, as well as the capacity to be welded. Cast aluminum alloys have been utilized extensively in the manufacture of aircrafts. They are preferred due to their significant strength-to-weight ratios. On the contrary, pure aluminum is very soft, and its softness means that it cannot be utilized for such activities (Eskin, 2008).

Comparison between Cast Aluminum Alloys and other Alloys

Cast aluminum alloys’ elastic modulus is estimated to be about 70GPa. This modulus is a third of those possessed by most alloys, including those if steel. This means that for the same amount of load, components made from aluminum alloys do experience greater elastic deformations that most other alloys even when the components are of the same shape and sizes.

With regard to the manufacture of brand new metallic components, design choices are guided by the manufacturing technology selected. Extrusions have been found to be important since it is easy to extrude aluminum alloys for the purpose of forming complex profiles. It has generally been established that lighter and stiffer designs are achievable through the use of cast aluminum alloys (Persson, 2011).

A bicycle frame made from aluminum is able to utilize tubes with large diameter, and this cannot be achieved where other materials are utilized. In addition to yielding the desired strength and stiffness, the bicycles are also light in weight. With regard to the automotive engineering, vehicles manufactured from cast aluminum alloys facilitate the employment of space frames, and this ensures rigidity (Persson, 2011).

The Common Commercial Uses of Cast Aluminum Alloy

Aluminum cast alloys are utilized in the manufacture of automotive engines. This is especially the crankcases and cylinder blocks. Since a cast aluminum alloy is vulnerable to warping, especially at high temperatures, it is important for the engines to be installed with effective cooling systems. Metallurgical advancements and manufacturing techniques have been found to be instrumental during the manufacture of automotive engines (Zolotorevskii & Belov, 2007).

One of the main structural limitations of cast aluminum alloys is low fatigue strength, especially when compared with such other alloys as steel. Assessing the cast aluminum alloys in controlled condition in a laboratory indicates that they continue to weaken as the stress they are exposed to increases. The stress experienced when aluminum is overheated can be relieved through heat treatment before it is gradually cools. This is meant to avoid distortions when the items have already been manufactured (Zolotorevskii & Belov, 2007).

Conclusion

The report has discussed a number of aspects relating to the cast aluminum alloys. According to the report, cast aluminum alloys are light on weight. Moreover, they are able to withstand high operating temperatures. Cast aluminum alloys are strong, corrosive resistant, and highly rigid. These characteristic features have made it possible for cast aluminum alloys to be utilized in multiple manufacturing activities. Aluminum has been utilized in computing and telecom industries. The alloys have been utilized especially where there is need to heat dissipation, EMI shielding, and durability (Warmuzek, 2004).

The paper has indicated that aluminum is not found in its pure form, and this is why it proves to be important to undertake the extraction process. Considering that cast aluminum alloys have important characteristic features, the process of extraction ought not to hinder the goal of using the element in manufacturing. Due to its excellent performance in the manufacturing industries, aluminum has been utilized widely. Users of the products attest that the items are utilizable even high operating temperatures. The products do also possess remarkable corrosion resistance; they are light in weight, and very strong. In conclusion, there has been remarkable progress towards the extraction of aluminum as well as casting (Eskin, 2008).

References

Eskin, D. G. (2008). Physical metallurgy of direct chill casting of aluminum alloys. Boca Raton: CRC Press/Taylor & Francis.

Persson, E. L. (2011). Aluminum alloys preparation, properties, and applications. Hauppauge, N.Y.: Nova Science.

Warmuzek, M. (2004). Aluminum-silicon casting alloys an atlas of microfractographs. Materials Park, OH: ASM International.

Zolotorevskii, V. S., & Belov, N. A. (2007). Casting aluminum alloys. Amsterdam: Elsevier.