Many industries are looking for innovative ways to reduce their costs, lower the weight of their products, and reduce their overall energy consumption. As a result, lightweight metals, such as aluminium, magnesium, and titanium are being increasingly considered to replace steel components.
With new research into alloys and surface technologies like PEO, engineers are able to use these lightweight metals in ways that would previously have been considered inappropriate. To find the right material solutions, it is important to have a sense of the potential advantages and drawbacks of each metal, and how they might impact on the project at hand.
Advantages of aluminium
Aluminium has long been used as an alternative to stainless steel, given its properties are highly favourable for a number of industrial applications. First and foremost, it is cheaper than steel to cast and fabricate, and the cheapest of the metals we’re looking at pound for pound.
Aluminium has a passive oxide layer which provides innate corrosion resistance, which can be further improved through alloying and surface coating. It is about a third of the density of steel, giving it a useful strength-to-weight ratio. This can easily be further improved through alloys and coating techniques.
Aluminium also has high ductility and malleability. As a result it can be precision machined with ease, saving time in the process of fabrication, making it a greener and more economic option.
Disadvantages of aluminium
Despite its advantages, it is worth keeping in mind that there are a number of drawbacks to using aluminium for certain applications.
Its low hardness tends to mean it has poor abrasion and wear resistance. Hence, hard wearing coatings are required in many circumstances to enable its use where it otherwise provides suitable mechanical properties.
While aluminium does have a fairly low tensile strength, there are alloys that can raise it from 70 MPa to around 700 MPa, providing a very high strength-to-weight ratio. However, it should be noted that the price for such high strength tends to be a significant loss of corrosion resistance. Coatings are normally essential to prevent corrosion where high-strength alloys such as 7xxx and 2xxx series are employed.
Although it is widely used in food packaging and cooking utensils, there is some concern about aluminium’s biocompatibility and potential links to Alzheimer’s disease. Again, protective coatings can provide the answer in many cases, helping to ensure no reaction of the substrate occurs.
Industrial uses of aluminium
From aircraft fuselage to coke cans, aluminium, with its low weight, low cost, and ease of fabrication lends itself to a myriad of engineering applications:
- Apple have led the way in the widespread use of aluminium to make the distinctive bodies of their MacBooks, iPhones, and iPads. Steve Jobs’ enthusiasm for the metal even led him to order a custom aluminium yacht. Since Apple’s pioneering use of aluminium, it is now the choice material for laptops and phones.
- Many cars have a lightweight aluminium hood and other body panels. Typically, major engine components such as engine blocks and pistons are now almost exclusively made from cast aluminium alloys. Other lightweight aluminium components such as brake callipers, electrical housings, interior trim parts all help to reduce vehicle weight and increase fuel efficiency.
Advantages of magnesium alloys and coating
A surge in interest over the past decade has revealed how magnesium alloys and coating techniques can make the most of the metal’s attractive properties.
Magnesium is extremely light: it has a density of 1.74 g/cc and is 75% lighter than steel, 50% lighter than titanium, and 33% lighter than aluminium, offering serious opportunities for efficiency savings in applications using it.
It has the highest known damping capacity of any structural metal, capable of withstanding 10x more than aluminium, titanium, or steel thanks to its high mobility dislocations. It is also very easy to machine, and can be injection moulded. Additionally, magnesium is entirely biocompatible, posing no toxicity hazards – offering an immediate advantage over aluminium.
Disadvantages of magnesium alloys and coating
However, magnesium has some well known shortcomings that limit its wider applicability in industry.
For one, it is highly chemically active, meaning chemical and corrosion resistance tends to be low. Its low surface hardness, like that of aluminium, makes it difficult to use in tribological applications without a coating.
Potential concerns about flammability also often rule out the use of magnesium, but only in extreme thermal conditions rather than most industrial applications. Nonetheless, this aspect should still be considered as part of a holistic material selection process.
Making magnesium fit for industrial applications
Since the 1998 ACEA agreement, legislation limiting carbon emissions has led the automotive industry to investigate ways in which the extremely light weight of magnesium can be made fit for purpose. Prior to this surge in interest, magnesium had seemed unusable in many industrial contexts. However, recently discovered alloys have provided the surface characteristics for the metal’s successful integration into automotive designs.
Higher-purity variants of traditional alloys have resulted in a significant resistance to corrosion, and new coating techniques such as plasma electrolytic oxidation (PEO) make a thoroughly resistant neutral oxide from the metal’s substrate. Magnesium’s poor creep resistance also traditionally made it unsuitable for high temperatures, but recently discovered alloys such as ZE41 & ZWO8203 are heat resistant at extreme temperatures (c. 400 F).
Additionally, advanced surface coating technology like PEO can greatly enhance thermal and corrosion resistance, as well as providing a range of additional surface features to extend the life of magnesium alloy components.
As a result of these developments, magnesium is increasingly being used in a range of settings:
- Car seats, power tools, luggage, and cameras have all been designed to make the most of lightweight, strong magnesium.
- Military engineers have begun using magnesium in helicopter gearboxes and generator housings, as a means of providing lightweight resistance to extreme temperatures.
- High-performance mountain bike frames and wheels are increasingly made of lightweight, corrosion-resistant magnesium.
- The aviation and automotive industries are increasingly looking at ways magnesium can increase fuel efficiency and reduce greenhouse gases.
- Complex, light, and strong components such as those found in engines can easily be moulded out of magnesium.
Exciting developments in magnesium alloys, manufacturing methods and coating technologies are making magnesium an increasingly viable candidate for a strong, lightweight, and cost-effective solution.
Advantages of titanium
Titanium is significantly stronger (220 MPa) than both aluminium and magnesium, although its higher density means that strength-to-weight ratios for the three metals tend to be similar. It is often the first port of call for engineers looking to replace steel in a lightweighting exercise for stressed components.
Titanium has the additional advantages of being highly corrosion-resistant and having an innate resistance to extreme thermal environments, reaching highs of approximately 550°C before mechanical performance deteriorates. Both these features are present without the use of alloying, and can be enhanced further when alloys are introduced.
Disadvantages of titanium
Titanium plates and components often run into the complication of cracking. They are sensitive to fatigue, especially in the cases of the notch sensitivity effect; areas of geometric discontinuity have a detrimental effect on the fatigue strength of the metal, causing it to crack.
Titanium also has a high cost of extraction and fabrication, which may rule out its use for the general consumer market and a number of industries.
Industrial applications of titanium
In industry, titanium can be found:
- On ship hulls, submarines, and other structures exposed to seawater, due to its high corrosion-resistance
- In hip replacements and dental implants, due to its high biocompatibility and strength.
- In aircraft, spacecraft, and missiles.
In industry, titanium can be found:
If money is no issue, titanium is an excellent choice for a strong, lightweight material. This is only enhanced with the use of advanced surface coating like PEO that can eliminate its susceptibility to cracking and enhance its already prominent features..
Integrate lightweight metals seamlessly into your designs with PEO
Aluminium, magnesium and titanium each showcase unique properties that can bring certain optimisations to specific designs. But one thing they all have in common is the ability to reduce the weight of designs, which is a design challenge that permeates through almost every sector of engineering.
Like their benefits, each of these metals showcases certain weaknesses to different environmental and mechanical elements. As a solution, PEO’s advanced electrolyte bath process provides a protective outer ceramic layer that provides a number of customisable surface characteristics; hardness, corrosion resistance, thermal protection, dielectric strength, enhanced adhesion and many more.
To find out more about the PEO process and how it can enhance the properties of aluminium, magnesium and titanium for your design, send an enquiry today.
FAQ
Which metal is best for high thermal applications?
Titanium is the best of the three metals for high thermal applications. That said, certain magnesium and aluminium alloys can greatly enhance thermal performance. When paired with PEO, these metals can also exhibit mechanical performance in extreme temperatures.
How sustainable is each metal?
All three metals can be 100% recycled naturally, however certain coating solutions such as chromate conversion processes prevent their recyclability and can produce harmful byproducts. PEO is free of organic compounds, COV or strong acids and enables full recyclability of components.
What is the application of magnesium alloy in aerospace?
With thorough coating solutions such as PEO, magnesium can be used in a variety of structural and internal components in aerospace applications to optimise weight and enhance fuel efficiency. Keronite’s PEO technology was chosen as the coating technology for NIRSpec after extensive mechanical and thermal testing
How effective is each metal for structural applications?
Each metal can be integrated into structural components with varying degrees of success, with magnesium having the lowest tensile strength and titanium exhibiting the highest. With PEO, the structural capabilities of each metal can be enhanced to be successfully integrated into a number of structural components.
What is magnesium alloy used for/what are magnesium alloy applications?
Various magnesium alloys provide specific characteristics; high-pressure die casting provides extreme thermal resistance, ultrastrong alloys provide extreme tensile strength, and high-heat conductivity alloys enable heat dissipation and management characteristics. This enables the use of magnesium in structural components, those within and close to engines and in heat management/dissipation systems. PEO enhances the characteristics of each alloy, greatly extending the life of these components.
Metal strength is among the most crucial mechanical properties, helping to classify metal applications. Thus, the importance of having the metal strength chart cannot be overemphasized. Some metals are more suitable for the aerospace industry, while others are ideal for electronic components.
The metal strength chart is a critical determinant that helps engineers, designers, and manufacturers choose the best metals for their projects. Understanding metal strength is crucial for making a choice.
Therefore, this article breaks down everything you need to know about metal strength. Read on to learn more.
Types of Metal Strengths: The Common Parameters Used
Materials show different types of strengths, regardless of their applications. The strength a metal exhibits will depend on the load applied and how the load is applied. The measure of strength will help you determine which metal material is best for specific applications.
Here are the different measurements of metal strength.
Tensile Strength
This type of strength refers to the maximum degree of stretching a metal can withstand before fracturing or damaging. Essentially, it measures how much tension such metal can withstand.
Furthermore, it is an excellent point of reference to know the performance of metal during application. A metal that passes its yield point upon the application of external forces may show permanent or temporary deformations.
There are three further divisions of tensile strength, namely:
- Yield Strength. This refers to the maximum strength point of a metal. It is the load the metal can withstand before exhibiting plastic deformation. Manufacturers use the yield point to determine the maximum load a material can take. It also provides a suitable means to define failure in engineering codes.
- Ultimate Strength. It describes the maximum tensile, shearing, or compress stress a metal can ensure without deformation or breakage.
- Breakable Strength. This refers to the stress coordinate you will find on the stress-strain curve whenever a metal fails.
Impact Strength
Impact strength measures the degree of impact or sudden force a metal can endure before failing. The limit of a metal and its impact load is expressed in terms of energy.
Thus, impact strength also helps measure how much energy a metal can absorb before fracturing, tearing, or damaging.
One of the most common misconceptions in the manufacturing industry is that a high impact strength would be equivalent to increased material hardness. However, this is not always the case.
Some factors may affect impact strength. Such factors include temperature, material thickness, and notch radius, tilting the favor towards metal hardness.
Compressive Strength
As you may have guessed from the name, compressive strength is the maximum amount of compression or pressure that metals can withstand without damage.
A universal testing machine often helps in testing the compressive strength of metals. The machine applies increased load on the material until the metal starts deforming.
The tester may apply the load on the bottom and top of the metal. The point where deformation begins to occur gives manufacturers a view of the compressive strength of that metal.
Why Do We Need to Learn About Metal Strength?
Sheet metal fabrication and other related techniques go beyond using any available material. It is more about using the correct type of metal. Considering the strength of metal will help you know if it is suitable for your application.
Here are some reasons why strength is an essential factor in manufacturing:
Structural and Mechanical Design
Engineers and designers need to understand their components’ strengths when it comes to structural and mechanical elements. This knowledge will help you identify the exact point where the metal can potentially fail or break.
Thus, you will have the opportunity to set limits while also defining necessary constraints for designed parts.
Material Selection
Metal strength determines if your machined component will serve its purpose effectively.
A structure may easily deform if you use metal with low strength for an application that requires a high-strength metal. For instance, heavy-duty machine parts will require high-strength metals. In such cases, steel, titanium, tungsten, etc., are often the best choices.
Using low-strength metals for such parts will render them useless for their intended applications. This will result in a waste of effort, time, and resources.
Durability and Safety
As mentioned earlier, metal strength is a measure of the level of impact the metal can take before losing shape. Therefore, it determines the durability of parts made from such metals.
This is crucial, especially for parts that may be subjected to high-stress applications. Furthermore, the strength of metals helps to set manufacturing limits. This way, you can avoid application failure.
Understanding the strength rating of metals ensures the safe design of components. You will also be sure that such elements can adequately support intended loads without harming users.
What Are the Strongest Metals Used in Metal Fabrication?
While several metals are used in sheet metal fabrication, their strengths differ. There are stronger options that manufacturers prefer, depending on design requirements and applications.
Here are some of the strongest metals commonly preferred in manufacturing:
Carbon Steel
This is one of the commonest alloys of iron and carbon, and it rates high for every quality that defines a metal’s strength. Yield strength of 260 MPa and tensile strength of 580 MPa puts it among the strongest metals. It also has high impact resistance.
Manufacturers can fabricate carbon steel into various hardness levels. This often depends significantly on the carbon content. As the carbon quantity rises, the steel strength increase.
Carbon steel is an excellent option for construction purposes and other appliances.
Stainless Steel
This is a corrosion-resistant alloy of steel, manganese, and chromium. It has a yield strength of about 1,560 MPa and tensile strength of 1,600 MPa.
As with the various steel options available, it highly impacts resistance. One of the unique features of stainless steel is its distinctive silver mirror coating. This metal is lustrous and brittle, and it does not tarnish upon air exposure.
Some stainless steel applications include cookware, surgical instruments, metal ceramics, appliances, etc.
Tungsten
Tungsten boasts the highest tensile strength among naturally occurring metals. With an ultimate tensile strength of 1,725 MPa, many people tag it the toughest and strongest naturally occurring metal.
It is metallic and grey in appearance, and it is often brittle. However, tungsten often comes alloyed with other elements to compensate for its brittleness. One of such alloys is tungsten carbide, which is usually harder.
The strength of this metal makes it helpful in making military components. It is also valuable in aerospace, mining, and other industries.
Titanium
This is another strong, naturally occurring metal with a high tensile strength to density ratio. It is more famous for its low strength-to-weight ratio and increased corrosion resistance.
This advantage makes it an ideal option for the aerospace and automotive industries. It is also useful for medical and military applications.
Titanium Aluminum
Asides from titanium in its pure state, it is often alloyed with other elements, further enhancing its strength.
Titanium aluminide is one of the strongest of these alloys. It contains aluminum and vanadium, with a tensile strength of 880 MPa and yield strength of 800 MPa.
Chromium
Chromium makes this list because many people consider it the hardest metal available. It may not have similar strength as other metals, but it offers a significant advantage when alloyed with other metals.
It is a key material for manufacturing stainless steel, a top-rated metal in various industries.
Iron
Iron is the go-to option for rifle barrels, bicycle chains, cutting tools, etc. It completes this list of the strongest metals for fabrication with a yield strength of 246 MPa and tensile strength of 414 MPa.
Metal Strength Chart
When machining metal parts, you need to know some essential parameters. We have discussed yield strength, tensile strength, compressive strength, and impact strength in the earlier part of this article.
The metal strength chart helps you further narrow down your choice. It enables you to compare the properties of various metal materials. This will ensure that you select the right option for your application.
Below is the metal strength chart:
Types of MetalsTensile Strength (PSI)Yield strength (PSI)Hardness Rockwell (B-Scale)Density (Kg/m³)Stainless steel 30490,00040,000888000
Aluminum 6061-T645,00040,000602720
Aluminum 5052-H3233,00028,000–2680
Aluminum 300322,00021,00020 to 252730
Steel A3658-80,00036,000–7800
Steel Grade 5065,00050,000–7800
Yellow Brass–40,000558470
Red Brass–49,000658746
Copper–28,000108940
Phosphor Bronze–55,000788900
Aluminum Bronze–27,000777700-8700
Titanium63,00037,000804500
Conclusion
Selecting the suitable metal for your project is very vital. It determines where such a part will meet design requirements or fail. Once you know the purpose of your intended part, the metal strength chart will help you make the best choice.
However, you can contact AT Machining whenever it gets complicated. Our extensive experience in metal machining will help us bring the best out of your project.
FAQs
Is titanium stronger than steel?
Titanium is generally stronger than many grades of steel. When it comes to sheer strength, you should choose the best titanium alloys as opposed to low to medium steel grades. However, using the highest stainless steel grade will be a better option than titanium in terms of strength.
What is the difference between metal strength and hardness?
Strength refers to the metal’s ability to withstand an external load without deformation. On the other hand, hardness is the ability of a metal to resist scratching or penetration. Knowing metal strength will help you set limits on the maximum allowable load on components. This will help avoid damage to machinery and structures.
On the other hand, hardness indicates the resistance of the metal to mechanical wear. Manufacturers prefer harder metals for parts required to withstand high stress.