Properties of Aluminum
Aluminum stays soft if cooled suddenly, and becomes hard if cooled gradually. Because of this property, it’s used in very important applications. This article contains detailed information about the properties of aluminum. The topics covered are as follows:
Aluminum’s Purity Grade:
Aluminum, which has begun to replace cast iron, wrought iron, and steel in general industry, holds an important place in the electrical and food industries. Aluminum used in the electrical and food industries has a purity grade of 99.99%. Aluminum material is produced at purity grades of 99.0, 99.5, and 99.99%.
Physical Properties of Aluminum:
Specific gravity of aluminum:
Cast aluminum: 2.65 = 269 g/cm³
Wrought (rolled): 2.7 g/cm³
Aluminum’s melting point (melting temperature): 658°C
Aluminum’s boiling point (boiling temperature): 1800 °C
Thermal conductivity coefficient: 173
Thermal Expansion:
At 0-50 degrees, 1.17 mm/m
At 100 degrees 1.38 mm/m
At 200 degrees, 4.94 mm/m
At 400 degrees, 10.60 mm/m
At 500 degrees, 13.70 mm/m
Shrinkage rate: 1.7% – 1.8%
Volume increase when going from solid to liquid: 6.5%
Strength Properties of Aluminum
This depends on the material’s purity grade and manufacturing method.
When discussing the properties of aluminum, its strength properties can’t go unmentioned.
The dynamic strength of pure aluminum is approximately 0.4-0.45 times its static strength. If cold-worked aluminum is welded, the strength of the transition zone decreases. Metals regain the strength they gained through cold working (such as cold rolling and drawing) once annealed. Since the workpiece is also annealed during welding, its strength decreases as well. If the part is cold-hammered after cooling down following welding, it regains its former strength. Care must be taken during this hammering not to lose any of the part’s thickness.
Aluminum’s Cold-Working Property
If aluminum is cold-worked at room temperature, its tensile and yield strength increase. However, its elongation and ability to deform further decrease. This increase and decrease depend on the degree of deformation (rolling reduction). Based on the degree of deformation, aluminum is classified into tempers such as soft, 1/16 hard, 1/8 hard, 1/4 hard, and 1/2 hard.
Hard (that is, cold-worked) aluminum has lower corrosion resistance than soft aluminum. For example, an aluminum with a purity grade of 99.5%, which has a tensile strength of 7 kg/mm² and an elongation of 35%, will see its tensile strength rise to 10 kg/mm² and its elongation drop to 15% if subjected to 20% cold working. If the degree of deformation rises to 40%, the strength reaches 12 kg/mm² and the elongation drops to 12%.
Aluminum’s Hot-Working Property
Hot working of aluminum (such as hot bending of pipes, sheets, and profiles) is always possible. A previously cold-worked aluminum workpiece can also be hot-worked. But, just as in welding, its strength decreases; the hot-working temperature is between 300-400 degrees.
Aluminum’s Corrosion Resistance
Does aluminum rust?
Corrosion resistance is also among the properties of aluminum. Aluminum has a strong affinity for oxygen. It combines with oxygen in a short time to form alumina (Al2O3); over time, aluminum exposed to air combines with oxygen and its entire surface becomes covered with a gray layer of alumina — this property of aluminum increases its resistance to corrosion. This oxide layer that forms can’t be removed by washing with water. This property of aluminum has broadened its range of applications. Cold working reduces corrosion resistance. As aluminum’s purity grade decreases, its corrosion resistance also decreases. In other words, foreign elements reduce corrosion resistance.
In this article, we’ve tried to provide information about aluminum. We’ve presented technical information about the properties of aluminum. Until we meet again in a new article.
Lightweight Metal Property
Since aluminum has about one-third the density of steel, it’s preferred for lightweight constructions.
Natural Oxide Layer
Thanks to the thin oxide layer that forms on its surface, aluminum protects itself from corrosion.
High Thermal Conductivity
Since aluminum is a good heat conductor, it’s widely used in manufacturing radiators and coolers.
Related Questions
The cooling rate determines how aluminum’s internal crystal structure forms. Rapid cooling prevents the atoms from forming an ordered structure, leaving the material soft, while slow cooling allows a harder internal structure to form.
In these sectors, properties like conductivity or chemical inertness are critically important, and even a small drop in purity can negatively affect these properties. High purity guarantees the material performs reliably and consistently in these sensitive applications.
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