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What Is a Light Metal?
Light metals have high strength-to-weight ratios and low density compared to the density of steel, which is approximately 7.8g/cm3. Magnesium, titanium, and aluminum are the widely used steel alternatives with low density and significant commercial importance.
Magnesium and its alloys exhibit the lowest density; titanium offers good corrosion resistance with remarkable strength, while aluminum is the most versatile and adaptable material. These three metals are obtained from the earth’s crust and further enhanced for improved properties. More notably, they are typically malleable, corrosion-resistant, lightweight, and ductile.
Typical Lightweight Metals
Various metals fall in the category of light metals. We’ll discuss the common light metals used in engineering applications below:
Magnesium
Magnesium is a commonly available lightweight, non-ferrous, and older structural metal. Magnesium and its alloys provide moderate strength, low density, excellent corrosion resistance, and good ductility. Magnesium alloys have no specific yield point and are susceptible to scratches and other stress-raisers, which could significantly affect their endurance limits. Magnesium has a similar melting point range as aluminum at 650°C (1202°F) and 660°C (1220°F), respectively.
Magnesium-base metals exhibit high unit resilience and low modulus of elasticity. Modern magnesium alloys and coatings help enhance the strength and durability of magnesium products. Despite its high machinability, magnesium machining generates highly combustible dust. Typical applications of magnesium include performance automotive parts, bicycle frames, sporting and recreational equipment, and consumer products.
Production of Magnesium and Magnesium Alloys
Magnesium is compatible with various techniques, including high-pressure die casting, casting, permanent mold casting, and semi-solid casting. Most manufacturers utilize die-casting techniques when working with magnesium. Magnesium die-casting allows the creation of thin-walled components with intricate features at high speed. Product manufacturers use hot and cold chamber machines for magnesium. Machining experts recommend higher shot speeds for magnesium to attain optimal performance for thin-walled components.
Unlike traditional die-casting techniques, vacuum die-casting is a typical variant of the die-casting process that manufacturers use to produce parts with improved properties and reduced porosity. However, several factors must be considered when determining production techniques and alloys for magnesium casting to achieve superior-quality components at a low cost. Tooling costs, end-use applications, and post-casting operations are typical variables.
Titanium alloys
Titanium (Ti) is a shiny transition metal with a silver color, excellent corrosion resistance, outstanding strength-to-weight ratio, and relatively low density compared to other metals. It is the strongest and heat-resistant metal of the three and stands out for its high biocompatibility and corrosion resistance, making it highly compatible with any chemical process. Hence, it is widely embraced in marine equipment, aerospace applications, chemical processing equipment, sports equipment, marine applications, orthopedic devices, and dental implants..
Titanium and its alloys are the first alternative to steel that manufacturers consider when they need high-performance, lightweight components. Titanium components exhibit high resistance to extreme thermal environments. Titanium can withstand up to 550°C before its mechanical performance deteriorates.
Production of Titanium and Titanium Alloys
The Kroll process is the standard titanium and titanium alloy production process. It involves treating the principal ore rutile with chlorine gas to make titanium tetrachloride, purified and reduced to a metallic titanium sponge through reaction with magnesium or sodium.
Manufacturers subject the titanium sponge to an alloying and melting process, which is often laborious and expensive. However, experts developed an alternative method to produce high-quality titanium alloy powders. It enables the effective processing of this metal into commercial products. Nevertheless, several steps are involved in converting purified titanium sponge to a suitable form for structural applications.
Titanium manufacturers utilize an argon or vacuum environment to consolidate purified titanium sponges into ingots. Manufacturers often compress and weld titanium sponges, alloying elements, and recycled scrap mechanically into an enlarged, cylindrical electrode, which melts in a copper crucible when electricity passes through it. The titanium ingot is melted again the same way to ensure the uniform distribution of the alloying elements.
Aluminium Alloys
Aluminum is a robust, non-ferrous metal that is intrinsically soft with various highly favorable properties, making it a suitable material for industrial applications. Aluminum and aluminum alloys exhibit excellent electrical conductivity, thermal conductivity, and corrosion resistance. Although the extraction and processing of these materials require high energy consumption, they are environmentally friendly and recyclable. Moreover, aluminum is a long-term stainless steel alternative. It exhibits high machinability ratings and can be easily cast into different structures.
Aluminum alloys are extremely light weight metals for different purposes across industries like electrical, construction, and transportation. Some aluminum alloys offer great strength similar to that of carbon steel. The 6061 alloy is a common aluminum alloy with extensive applications due to its unique combination of properties. Typical uses of aluminum include medical implants and prosthetics, electrical wires, beverage cans, window frames, automotive parts and aerospace components. More notably, aluminum’s passive oxide layer protects its surface from corrosive substances. Also, you can enhance its innate corrosion resistance properties through surface coating techniques and alloying.
Production of Aluminum and Aluminum Alloys
Manufacturers use casting, rolling, extrusion, drawing, and forging techniques to produce aluminum and its alloys. Besides, specific processes are more suitable than others due to the varying composition of aluminum alloys.
However, the hot extrusion of aluminum is widely embraced since it enables the production of almost any kind of shape in a cross-section. The process involves mounting a preheated billet on the press container and using a ram to press it through the shaped steel die. Although the extrusion process suits most aluminum alloys, the 6000 aluminum grades are primarily from commercial extrusion. Hence, it offers a peak combination of ease of extrusion and speed with the flexibility to attain thin sections and complex shapes with the desired surface finish.
Common Ways of Processing of Light Metals
Light metals are compatible with a wide range of processing techniques. We’ll explore the different ways manufacturers process lightweight metals into preferred end-use products below:
Forming
Forming is a standard metal processing technique involving a series of processes to change metal into a usable form. It comprises methods such as bending, extrusion bending, roll bending, brake bending, and press drawing. The forming process occurs at higher temperatures for all metal types. Bending is the commonly used process for forming magnesium sheets and extrusions. However, the bend radius is critical in magnesium sheet bending operation.
Powder Processing
Powder processing involves applying heat, pressure, or both to the powder to form hard components with internal mixtures that provide new, essential product properties. The powder is created by melting metal and forcing it through a nozzle while exposing it to a water spray or inert gas, breaking the metal into tiny droplets, which are later cooled to form a powder. Then, the metal powder is sprayed, pressed, or extruded to make blanks for further shaping or molding different shapes as almost finished parts.
Melt Processing
Melt casting is a versatile metal processing technique. It involves filling a die or mold with molten metal and cooling it while the component hardens. Although it is an aged process, it offers exceptional potential to reduce metal structure weight. Thin-wall, dissimilar-metal, and high-integrity casting are three advanced melt processing methods.
- Thin wall Casting: It is compatible with different metals, including steel and aluminum. However, complications like preventing the metal from solidifying untimely and maintaining uniform flow can occur when working with molten metals.
- Dissimilar Metal Casting: This technique combines two or more metals in a single casting, providing considerable benefits. It ensures the various mechanical properties of the mixed materials are employed where required. Likewise, a product can be cast with parts formed from a specific metal while the other parts are made from another metal.
- High-Integrity Casting: Here, you can easily make a particular product to meet unique standards and requirements without microstructures and porosity present in the cast part.
Thermo-Mechanical Processing
Thermo-mechanical processing, or TMP, is a metal processing technique that enhances metals’ material properties. It creates lightweight components with intricate designs at lower manufacturing costs. This technique involves the simultaneous control and use of thermal and deformation processing to develop components and materials with enhanced properties and deliver optimal performance.
The TMP process offers seamless controls at each stage. The temperature and shaping time are controlled concurrently, as well as the amount of deformation at each step of the process and how the cooling is controlled. Therefore, engineers can exploit each material’s microstructures in several ways due to the ability to control heating, forming, and cooling at each step.
TMP ensures better control over the end product since it prevents the need for further reheating and quenching steps. Hence, it makes the production process more efficient and cost-effective. Thermo-mechanical processing provides improved properties for titanium alloys, aluminum alloys, and other light metals. It enhances the material’s resistance to fatigue-induced degradation, strength, and resistance to fracture.
CNC Machining
CNC machining of light metals such as aluminum, titanium, and magnesium refers to the process of machining these materials through the use of computer numerical control (CNC) technology to provide the desired cut shape for a metal part.CNC (Computer Numerical Control) programming involves the use of a computer code to specify each of the machining tool’s movements so that they can be repeated with great precision.
As many scholars have pointed out, aluminum is easy to machine and has good corrosion resistance, especially after anodizing aluminum parts can withstand salt spray testing for 24-48 hours. Titanium is favored in cutting-edge fields for its heat resistance and strength, but machining with titanium can be a challenge due to the hardness of the material and the need to manage tools effectively. Magnesium is the lightest structural metal and therefore enjoys the benefits of CNC machining, but flammability must be considered. CNC machining receiving and cutting processes ensure that material utilization is maximized, losses are minimized, and parts are manufactured for use in the aerospace, automotive, and medical industries.
Helpful Considerations for Choosing the Best Light Metal
These three metals offer excellent means of reducing the weight of your product. You might want to consider several factors to effectively choose the suitable material that meets the demands of your applications. Below are some of these factors:
Examine the Material Properties
Understanding the mechanical properties of light metals such as titanium, aluminum, and magnesium is crucial since each differs in corrosion resistance, fatigue resistance, hardness levels, and tensile strength. Assess each material’s mechanical properties based on the demands of the intended application.
Titanium has the highest yield strength and good fatigue properties, which makes it the perfect option for applications requiring parts with high strength and durability. Titanium and aluminum exhibit high corrosion resistance and are suitable for applications that subject parts to harsh environments and substances.
Costs/Budget
Cost/budget is a significant factor that influences a material’s choice. As such, it is essential to consider what lightweight, strong metal fits within your budget range. Consider the cost of procuring raw materials, processing, fabrication, and finishing each material. Then, determine the one that best matches the budget. Although titanium is primarily expensive, magnesium is an ideal alternative, while aluminum is the cheapest.
Sustainability or Environmental Impact
You may need to examine the environmental effect of each metal throughout its life cycle, from its extraction stage to its ready-for-use stage. In addition, choose a metal that meets the industry’s standards and environmental regulations. However, light metals like aluminum and magnesium possess high recyclability, supporting sustainable practices.
Manufacturing and Processing
When determining the suitable metal for your project, the machinability, formability, and compatible joining techniques are critical considerations. Ensure that the intended metal can be effectively joined using the processes suitable for your project, such as adhesive bonding, welding, or riveting. While aluminum and its alloys exhibit high formability, magnesium and aluminum possess good machinability ratings.
Conclusion
Light metals like titanium, aluminum, and magnesium are common materials science and engineering use in fabricating lightweight structures. However, choosing the suitable material requires a delicate balance of corrosion resistance, strength, cost, weight, and machinability. Whenever you need the help of experts to choose a light metal for your project, AT Machining is the perfect partner to turn to.
AT-Machining offers extensive manufacturing solutions and other value-added services for all your manufacturing needs. Our expert engineers and machinists leverage our modern CNC facilities and expertise to deliver top-notch lightweight metal parts that meet stringent industry standards. Kindly contact us now to speak to our experts on how to elevate your project!
