Difference Between Cast and Wrought Aluminium Alloys

The key difference between cast and wrought aluminium alloys is that the cast aluminium alloys have many internal and external defects whereas the wrought aluminium alloys are normally free of internal and external defects.

Aluminium alloys are the alloys of aluminium that contain aluminium as the predominant metal along with one or more alloying elements such as copper, magnesium, silicon and tin. There are two major forms of aluminium alloys. Namely, they are cast and wrought aluminium alloys.

CONTENTS

1. Overview and Key Difference
2. What are Cast Aluminium Alloys
3. What are Wrought Aluminium Alloys
4. Side by Side Comparison – Cast vs Wrought Aluminium Alloys in Tabular Form
5. Summary

What are Cast Aluminium Alloys?

Cast aluminium alloys are the alloys containing aluminium as the predominant metal and some other alloying elements. We can divide this group of alloys into two major groups as heat-treatable and non-heat-treatable forms. Also, the tensile strength of these alloys is lower comparatively, but they yield cost-effective products. It is because of their low melting point. The most commonly used form is aluminium-silicon cast alloy. There, high levels of silicon provide the alloy with great casting characteristics.

We can list out the favourable properties of aluminium alloys that make them useful as cast aluminium alloys.

• Low melting point
• Good fluidity
• Capability to control the grain structure
• Good surface finish
• Low solubility of gases
• Ability to strengthen by heat treatment

However, there are some disadvantageous properties as well. For example, these alloys show high shrinkage and susceptibility to shrinkage defects. Moreover, these alloys have a high solubility of hydrogen gas. And also, they are susceptible to hot cracking and has a low ductility as well.

What are Wrought Aluminium Alloys?

Wrought aluminium alloys are a form of aluminium alloys containing aluminium as the predominant metal. These alloys are mainly useful in shaping processes such as rolling, forging and extrusion. Also, we can divide this alloy form too into two major groups as heat-treatable and non-heat-treatable alloys. About 85% of the aluminium alloys are wrought alloy forms. They have a high tensile strength comparatively.

Heat-treatable forms can be strengthened by heat treatment processes. It is because the solubility of alloying elements depends on the temperature. The initial strength of these alloys comes from alloying elements such as copper, silicon, magnesium and zinc. Non-heat-treatable forms, on the other hand, cannot be strengthened by heat treatment. Their initial strength is due to alloying elements such as manganese, silicon and magnesium. Since heat treatment does not work on them, cold work or strain hardening can be used to strengthen the alloy. Moreover, these alloys are ductile and moderately strong.

What is the Difference Between Cast and Wrought Aluminium Alloys?

Cast aluminium alloy is a form of aluminium-containing alloy that has casting characteristics whereas wrought aluminium alloy is a form of aluminium-containing alloy that is useful for shaping processes. The key difference between cast and wrought aluminium alloys is that cast aluminum alloys have many internal and external defects whereas wrought aluminium alloys are normally free of internal and external defects. Furthermore, a  difference between cast and wrought aluminium alloys based on properties is that the cast aluminium alloys have a low melting point, hence, cost-effectiveness is high while the melting point is high for wrought form, thus, the cost-effectiveness is low.

Apart from that, there is also a difference between cast and wrought aluminium alloys based on their tensile strength. The tensile strength of cast alloy form is lower than that of the wrought form. The below infographic shows more details on the difference between cast and wrought aluminium alloys.

Summary – Cast vs Wrought Aluminium Alloys

There are two major types of aluminium alloys; cast and wrought aluminium alloys. The key difference between cast and wrought aluminium alloys is that the cast aluminium alloys have many internal and external defects whereas the wrought aluminium alloys are normally free of internal and external defects.

Reference:

1. “Aluminium Alloy.” Wikipedia, Wikimedia Foundation, 26 Oct. 2018. Available here 
2. “Materials Engineering.” Cast Aluminum Alloys [SubsTech], 4 Apr. 2013. Available here  
3. “Materials Engineering.” Wrought Aluminum Alloys [SubsTech], 28 July 2012. Available here  

Image Courtesy:

1.”Bootie bicycle frunt wheel balloon tyre bootiebike com”By Conollyb – Own work, (CC BY-SA 3.0) via Commons Wikimedia  
2.”Mig-29 on landing”By Dmitry A. Mottl – Own work, (CC BY-SA 4.0) via Commons Wikimedia