What Are Metal Alloys?

Metal alloys are the unsung heroes of our daily lives and shape civilisation around us – but what exactly are metal alloys?

A metal alloy is created when at least one pure metal is mixed with another mineral, which can be metallic or non-metallic, to change or improve certain qualities of the metal.

From jewellery to sturdy tools that enable us to work, metal alloys are the creation of a new material that retains the characteristics of its parent materials. It can also inherit distinct properties making metal alloys useful for a variety of applications.

Special Metal Alloys has been supplying nickel alloys and stainless steels in the global metal markets for over 35 years.

Contact us online, or give us a quick call on +44 [0]161 278 2386 to find out more.

Interstitial metal alloys

This alloy is created by inserting smaller atoms of other minerals in the “spaces” (interstices) between the homogenous atoms of the metal.

In creating steel, very small carbon atoms are “fitted” in the interstices of an iron matrix to make the iron harder and stronger.

Substitutional alloys

The alloy is created by substituting some atoms of similar size in one mineral for some of those in the metal.

Bronze and brass are created by substituting either tin or zinc atoms for similar size copper atoms.

Stainless steel is an example of combining an interstitial and substitutional alloy. By substituting for example some chromium, nickel, and manganese atoms for some of the iron atoms, steel now becomes stainless steel.

Homogenous metal alloys

When the alloy is created in a single phase, the atoms are evenly distributed throughout the alloy, with fully closed pores, and the alloy is visually uniform in its appearance, it is called a homogenous metal alloy. Examples are brass and bronze.

Heterogeneous metal alloys

If the metal alloy is created in multiple phases forming different metallic grains within the microstructure of the metal, it is called a heterogeneous alloy. This structure is extremely rare because the smelting and mixing process mostly homogenises the structure and these metal alloys are usually only applicable in laboratories.

How is a metal alloy created?

The primary metal, known as the base or matrix, is traditionally smelted and mixed in various percentage ratios with one or more minerals (metallic or non-metallic) chosen for their qualities to enhance the base metal. The mixture is then cooled at room temperature to produce a metal alloy with enhanced qualities.

With modern technology, new methods have been developed, the most common of which is to pulverise the components of a metal alloy, mix them together and then fuse them with a combination of extreme heat and pressure.

Ion implantation is another modern method to create metal alloys for semiconductors, microchips, metal finishings, and laboratory work. It is a low-temperature process by which ions of one element are accelerated into a solid target to change the physical, chemical, or electrical properties of the target.

What is the difference between metals and metal alloys?

Pure metals have only one atomic component, whereas metal alloys have atomic components of two or more elements, which changes the microscopic structure of each of the component elements.

What is the purpose of creating metal alloys?

Even with some 70 metals occurring naturally, they cannot meet all the requirements of a modern age in their pure form. We use metal alloys in our daily lives, ranging from jewellery to cutlery, tools, building and construction materials.

Here are just a few of the reasons for creating metal alloys:

  • Metal is alloyed in different combinations and ratios to improve the strength, heat resistance, durability, ductility, and corrosion resistance of pure metals. Examples are alloy tubing, aircraft framework, nuclear, defence, and petroleum applications, desalination plants, etc.
  • They can be created to make rare or expensive metals more accessible and affordable. An example is alloying 24kt pure gold to create harder and cheaper 9kt gold for jewellery.
  • Specific metal alloys are often the only viable solution for specialist purposes such as tubes carrying a variety of corrosive liquids, bearings and gears, guns, surgical and other medical instruments, high-performance instrumentation, and soldering.

What are the most common types of metal alloys and what are they used for?

Nickel Alloys

Nickel is a very hard metal with good conductivity and a remarkably high melting point. It alloys freely with other metals such as iron, titanium, cobalt, aluminium, chromium, molybdenum and copper to give greater resistance to corrosion, and exceptional strength at extreme temperatures, low expansion coefficient, and shape memory.

The nickel content of the various alloys is carefully balanced and can be as low as 8 or 9% and as high as 83%.

1.   Nickel-Iron alloys are used particularly in transformers, inductors, magnetic amplifiers, thermostat rods, cryogenic tubing, magnetic shields, and memory storage devices, They come in a large variety of shapes and forms, as seals because of their pliability and low expansion coefficient, and where dimensional stability is required.

2. Nickel-Copper alloys are highly resistant to corrosion by alkaline solutions, salts, and seawater. They are commonly used in hydraulic tubing, brake tubing, valve components, seawater cooling and firewater systems, heat exchangers, condensers and piping, oil coolers, hydraulic tubing, and antimicrobial touch surfaces.

3. Nickel-Molybdenum alloys are highly resistant to acids. They are used mainly in the production of stainless steels, special steels and superalloys for solid solution strengthening, precipitation hardening, deoxidation, and desulphurization.

4. Nickel-Chromium alloys are highly resistant to corrosion at normal and extreme temperatures and resistant to scaling. They are mostly used for casting and wrought parts in high-temperature applications.

5. Nickel-Chromium-Iron alloys fall into two major groups, one with exceptional strength even at high temperatures, and the other group with exceptional resistance to acids and oxidizing agents. They are typically used in petrochemical furnace components and sheathing of electrical heating elements.

6. Nickel-Chromium-Molybdenum alloys have exceptional tensile strength and corrosion resistance, in particular to reducing and oxidising acids, making them highly suitable to be used in the oil and gas, energy, construction and automotive industries.

7. Nickel-Chromium-Cobalt alloys have exceptional strength and resistance to various forms of corrosive agents. They are primarily used for bearing assemblies, step soldering, and radiation shielding.

8.   Nickel-Titanium alloy (also called Nitinol) is one of the heterogeneous metal alloys that offer shape memory properties, regaining its original shape when reheated if it is deformed either through heat or elastic deformation. Examples of its use are spectacle frames and structural shock absorbers in tall buildings.

Stainless steel alloys

The general term stainless steel encompasses a variety of stainless steel alloys containing various elements such as chromium, molybdenum and nickel in different ratios and combinations. It is known particularly for its strength, durability, and exceptional resistance to corrosion and extreme temperatures.

The main types of stainless steel alloys are austenitic, ferritic, martensitic, and austenitic-ferritic. Available as tubing, flats, and a variety of solid shapes.

a. Austenitic stainless steel has a crystalline structure achieved by adding elements such as nickel, manganese, and nitrogen. Due to its excellent corrosion resistance and outstanding mechanical properties at high temperatures, it is widely used in both conventional and nuclear power plants, and in the aerospace, automotive, medical and industrial sectors.

b.   Ferritic stainless steel has a low carbon content, good ductility, high corrosion resistance, and is more economical than some of the other types. They possess good ductility, corrosion resistance, are suitable for cold working, and are more economical than austenitic and duplex grades. Ferritic Stainless Steel is mainly used in making automotive parts, industrial machinery, kitchenware, cookware, industrial piping and vessels, construction, and architectural facades.

c. Martensitic stainless steels are strong and therefore relatively light, making them very useful in automotive applications for door beams, vehicle bumpers, and frameworks.

d. Austenitic-ferritic (duplex) stainless steels are very strong and durable and have exceptional resistance to corrosion, making them the common choice for structural materials in the chemical and petrochemical industries, power plants, etc.

Super Alloys

Superalloys are also known as special metals, high-performance alloys, heat-resistant or high-temperature alloys because they can continue to operate optimally while retaining their strength, shape, stiffness, and dimensional stability at extremely high temperatures.

These properties, combined with their exceptional mechanical strength, resistance to thermal creep deformation, surface stability, corrosion, and oxidation, make them highly suitable for aerospace and marine applications such as turbine engines, and in the nuclear and petrochemical industries.

Superalloys are classified according to the dominant metal in the alloy and include iron-based, cobalt-based, and nickel-based superalloys.

Titanium alloys

Titanium alloys have a very high strength-to-weight ratio and are renowned for their exceptional resistance to corrosion and heat.

There are different types, with various grades, of titanium alloys to deliver unique properties. They typically contain varying quantities and ratios of nickel, aluminium, chromium, molybdenum, cobalt, vanadium, iron, manganese, niobium, tantalum, zirconium, and copper.

For interest, the α, α+β, and β categorisation of titanium alloys depends on their metallurgical crystal structure at room temperature.

The α (alpha) phase consists of a hexagonal close-packed structure and β (beta) of a body-centered cubic-packed structure.

They are typically used in the aviation, biomedical, surgical, and orthopaedic industries.

Other very common metal alloys

Carbon steel alloys

Carbon steel alloys are known for their mechanical strength and wear resistance at normal temperatures. Low-carbon alloys are typically used in the automotive industry for structural body shapes; medium-carbon alloys for railway wheels and tracks, gears, crankshafts, etc; because high-carbon alloys are very wear-resistant, they are typically used in toolmaking. 

Copper alloys

Both as an alloy base and pure metal, copper is highly resistant to corrosion, ductile, malleable, and an excellent conductor of heat and electricity.

The two main copper alloys are brass and bronze, used for ornamentation, valve seats, shaped into tubing to carry a variety of liquids and gases, condenser tubes, evaporators, taps and plumbing connections, marine work and much more.

Aluminium alloys

Aluminium alloys are sought for their strength-to-weight ratio, and high rust resistance, and are used widely in a variety of industries and for a multitude of applications, from household to industrial, aeronautical, automotive, construction, engineering, and furniture industries.

Aluminium alloys are used in wrought, cast, tubular, and flat conditions.

Duralumin

It is as strong as steel with excellent fatigue and low-temperature toughness but weighs only 1/3rd of the weight of steel. It can be heat treated to further increase its strength and has high machinability.

These properties make duralumin highly suited for the fabrication of aircraft and vehicle parts and for tubing in cryogenic tank structures.

Zinc Alloys are typically used for die castings and galvanising.

Tin alloys are typically used for solder and bearing linings.

Special Metal Alloys specialises in nickel alloys, super alloys, titanium, and stainless steels for a large range of industries and can help you find solutions to all your metal alloy requirements on a small or large basis.

We supply a wide range of nickel alloys from our central stock and can source whatever products or alloys you require from reputable mills, with remarkably short turnaround times.

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Contact us online, or give us a quick call on +44 [0]161 278 2386 to find out more.

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