Properties of Aluminum: Understanding Welding Materials

It’s not hard to understand why aluminum is such a popular metal, used across a remarkable range of industries. Its many characteristics make it one of the essential materials in the architectural, aviation, automotive, and appliance industries, to name a few.

The numerous noteworthy properties of aluminum and aluminum alloys allow for various applications. For example, aluminum alloys are among the easiest to form and machine because of their mechanical properties.

Observing aluminum's physical, chemical, and mechanical properties makes it possible to predict its behavior in specific environments and under stress. These performance indicators help architects, fabricators, and designers select the correct applications for aluminum, so let’s look at these properties to learn more about this versatile material.

What are the physical, chemical, and mechanical properties of aluminum?

Physical properties

The physical properties of aluminum refer to its form and structure before any chemical alteration.

  • Structure: Aluminum’s face-centered cubic structure remains stable until its melting point.
  • Surface: Aluminum’s surface is often reflective.
  • Color and state: Non-magnetic, solid, silvery-white with a slightly bluish tint.
  • Hardness: Pure aluminum is relatively soft but is strengthened when alloyed and tempered.
  • Ductility: High ductility means aluminum can be beaten thin.
  • Malleability: Highly malleable. Aluminum can be bent or shaped.
  • Conductivity: Aluminum is an excellent electrical and thermal conductor.
  • Corrosion: Aluminum has an oxide layer making it corrosive resistant.
  • Thermal expansion: Aluminum has a thermal expansion coefficient of 23.2, between zinc (higher expansion) and steel (half the expansion range of aluminum).
  • Density: Aluminum has a low density of 2.70, compared to steel’s 7.87.
  • Melting and boiling points: Aluminum has a melting point of approximately 1220°F and a boiling point of approximately 4,478°F.

The physical properties of aluminum explain its many applications. With its excellent strength, corrosion resistance, and ductility, aluminum can be a beverage can, foil, and irrigation tubing.

Polished aluminum has good reflectance, resulting in its use in various decorative and practical applications, such as appliances and lasers. And its nonferromagnetic properties make it appropriate for the electrical and electronics industries.

The thermal conductivity of aluminum alloys is ideal for heat exchangers, evaporators, electrically heated appliances, and utensils, while its structure contributes to excellent formability.   

Chemical properties

Chemical properties are an object’s characteristics or behavior as it undergoes a chemical change or reaction. These observations of disruptions at the atomic level occur during and after the reaction.

  • Oxidation: Aluminum combines with oxygen to form aluminum oxide after exposure to moist air.
  • Pyrophorus: In a powdered form, aluminum will catch fire when exposed to flame.
  • Occurrence: Aluminum occurs as a compound in bauxite ore.
  • Reactivity with water: Aluminum quickly reacts with hot water.
  • Reactivity with acid: Aluminum reacts with hot acids.
  • Reactivity with alkalis: Aluminum is reactive with sodium hydroxide.
  • Ability to form alloys: Hundreds of aluminum alloy compositions exist.

Aluminum’s chemical properties are unusual in many ways. For instance, reactivity to both bases and acids is uncommon for metals, and this must be considered when aluminum is used as a beverage container. Manufacturers must ensure the aluminum will not dissolve, so these cans have a thin liner to prevent corrosion.

Another unusual fact about aluminum is that it is nonpyrophoric, except in a powdered form. However, aluminum is flammable and considered a dangerous hazard in its powdered state.

Also, because aluminum combines readily with oxygen, it affects welding practices. The oxide layer on the aluminum surface melts at triple the temperature as the aluminum underneath, so thoroughly cleaning the aluminum before welding is a must.

Mechanical properties

Mechanical properties record a material’s relationship with stress and measure the degree of elasticity in response to an applied load.

  • Ultimate tensile strength: 13,000 psi
  • Yield strength: 5,000 psi
  • Elongation at break: 15% to 28%
  • Shear strength: 9,000 psi
  • Fatigue strength: 5,000 psi
  • Elasticity in tension: Aluminum has Young’s modulus of 10,000 kilopounds per square inch (KSI), while copper has 17,550 KSI and wood is 1,595 KSI

What makes aluminum a good welding material?

Since aluminum is about one-third the weight of steel, weight is a significant factor in why aluminum is suitable for welding. Reducing the weight of many products would be a start to addressing global fuel-efficiency concerns. Using aluminum weldments would result in lighter vehicles, planes, and boats, cutting fuel consumption by an estimated 60% or more.

Because aluminum does not rust easily, paint and other coatings would no longer be required to resist corrosion on fabrications. It retains good ductility at subzero temperatures, good electrical and thermal conductivity, and high reflectivity to both heat and light. Aluminum is more malleable than steel, which tends to get rigid and crack if overworked, meaning it can be shaped into any design imaginable.

MIG, TIG, carbon-arc, and other arc welding processes can weld aluminum and its alloys successfully. Pure aluminum can be alloyed with many different metals to produce a wide range of physical and mechanical properties.

What are common applications for welding aluminum?

Some people might question, “What can you make with aluminum?”

Although aluminum has universal applications in industries like construction, transportation, electrical, and consumer goods, its applications go well beyond the traditional. For instance, aluminum, being considered non-toxic and safe for human exposure, can be combined with hydrogen and oxygen to make aluminum hydroxide. This substance deepens the colors and shines on paints and powdered makeup products. 

Aluminum is also an ingredient in several medicines that treat heartburn, acid indigestion, sour stomach, acid reflux, ulcers, and gas. It’s even used in a topical medication to treat poison ivy reactions.  

Remember that aluminum is pyrophorus in powdered form, so it should be no surprise that very fine aluminum powder is the primary component in the pyrotechnic industry. It’s used to create all silver and white fireworks and sparklers, giving them their bang. 

NASA and other space organizations prefer aluminum for the same reasons airplane and vehicle manufacturers do. Aluminum alloys mostly make up the Mars space rover Curiosity. At a whopping $2.5 billion price tag, the project would not have been possible without the cost-effective use of recycled aluminum.

Most kitchens have more aluminum than you realize, with refrigerators, microwaves, dishwashers, and pots and pans containing aluminum. In other areas, wheels, transmissions, bumpers, and radiators are now aluminum. Even your iPhone is about one-quarter of aluminum alloy! 

Applications for welding aluminum are nearly infinite, with projects for beginners and seasoned veterans. Start with a simple tool storage unit, coin bank, or bonsai planter, and graduate to more challenging tasks like bicycle frames, dog pot planters, and welding art.

Once you are hooked on the joys of aluminum and aluminum welding, you will want a quality welding machine designed for aluminum welding but without breaking the bank. Look no further than the welding experts at PrimeWeld for the perfect machine for your following welding projects. Can’t decide whether to buy a TIG or MIG welder? No worries! Our welding experts will guide you to the best machine for your applications.

The bottom line

Aluminum is a versatile metal with several advantages, including being lightweight, strong, and flexible. It can be cast, melted, formed, machined, and extruded, meaning it can be manufactured into various shapes and fabricated for numerous uses.

Because of its many benefits, aluminum has become even more popular. The aluminum extrusion process has enabled it to be supplied in additional complex designs.

No matter which forms you prefer, aluminum will be the lightest, most vital, and most machinable choice for the money!

Thanks for reading.

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