Guide to Metal Composition

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Metallurgy is the study of how inter-metallic compounds affect the physical and mechanical properties of materials. The composition of a metal determines its suitability for specific applications. This article will improve your understanding of metal composition to help you make more informed decisions when choosing and working with metals.

Jump to a section: What is Metal Composition  | Types of Metals | Elements Commonly Used in Metals | Common Metal Alloys | How to Identify Metals |  Uses of Metals and Their Alloys | Factors That Impact Metal Properties |  Challenges in Metal Composition | Testing and Certification Standards | Environmental Impact | FAQ 

What Is Metal Composition?

Metal composition refers to the different elements that make up a metal or metal alloy. For example, pure copper is an element, but when combined with tin, it forms the alloy bronze, which is about 88% copper and 12% tin. The composition of a metal defines its characteristics and properties.

The Importance of Understanding Metal Composition

A metal's characteristics, such as its strength, hardness, malleability, and corrosion resistance, depend entirely on its composition. For example, reducing carbon content in steel and adding chromium creates stainless steel, which has greater resistance to corrosion and high temperatures.

Types of Metals

Metals are generally divided into two main categories: ferrous and non-ferrous. 

Ferrous Metals

In ferrous metals, iron is the primary element. The word “ferrous” is derived from the Latin word “ferrum”, meaning iron. 

Characteristics of Ferrous Metals

Ferrous metals have several defining characteristics:

• Magnetic properties
• Strength and durability
• Susceptibility to corrosion
• High melting point
• Alloying potential
• Cost effectiveness

Composition of Steel

Steel is an alloy made of iron and carbon combined with some other elements that enhance the resulting metal’s mechanical properties. 

Composition of Cast Iron

Cast iron is a group of iron alloys that contain high amounts of carbon. They are high strength but lack ductility. As the name suggests, cast iron can be cast and formed. It is also machinable.

Non-Ferrous Metals

Non-ferrous metals do not contain any significant amount of iron.

Characteristics of Non-Ferrous Metals

Non-ferrous metals have the following characteristics:

• Non-magnetic
• Corrosion resistant
• Malleable with high ductility
• Lightweight and low density
• Highly conductive to thermal and electrical energy

Composition of Aluminum Alloys

There are a wide variety of aluminum alloys available on the market. Some include:

• 1000 series aluminum, which has an aluminum content of at least 99% (essentially pure aluminum).
• 2000 series aluminum is alloyed with between 2% and 10% copper.
• 3000 series aluminum is alloyed with 1% to 1.5% manganese.
• 3000 series aluminum is alloyed with 4% to 12% silicon.
• 5000 series aluminum is alloyed with 0.5% to 6% magnesium.
• 6000 series aluminum is alloyed with both magnesium and silicon.

There are also many cast aluminum alloys on the market, such as aluminum-zinc, aluminum-copper, and aluminum-zinc.

Composition of Copper Alloys

It is possible to alloy copper with several other elements, which provides a wide variety of metals with unique properties. These alloys include:

• Brass, made of copper and zinc.
• Bronze, made of copper and tin.
• Copper-nickel alloys, made by combining copper and nickel.
• Copper-silver alloys, made using small amounts of silver.

Composition of Titanium Alloys

Titanium alloys often feature other elements to enhance titanium’s high strength with lightweight properties. Titanium alloys fall into three main categories based on their microstructure: alpha, beta, and alpha-beta alloys. 

The alpha phase is a closely-packed, hexagonal microstructure, characterized by high strength but low ductility.

The beta phase contains a body-centered, cubic microstructure, which results in an alloy with lower strength but higher ductility than its alpha titanium counterparts. 

Alpha-beta titanium alloys are a combination of alpha and beta microstructures, which provides the best of both worlds. Alpha-beta titanium alloys are typically stronger than pure titanium and have better ductility, malleability, and weldability.

• Alpha titanium alloys contain alpha-stabilizing elements like aluminum, oxygen, and zirconium.
• Beta titanium alloys contain beta-stabilizing elements, such as vanadium, molybdenum, and niobium.
• Alpha-beta titanium alloys combine both alpha and beta stabilizers. Common alpha-beta alloys include titanium (with a titanium content of 90% or greater), titanium alloyed with between 3% and 6% aluminum, and titanium with a vanadium content of between 2% to 4%.

Composition of Nickel Alloys

Nickel alloys are made of nickel combined with other elements to enhance specific properties, such as strength and corrosion resistance. 

• Nickel-copper alloys (like monel) are made of 65% to 70% nickel with 30% to 35% copper and small amounts of iron, manganese, and silicon. 
• Nickel-chromium alloys (such as inconel) contain 30% to 45% nickel with 19% to 29% chromium and often small amounts of iron. 
• Nickel superalloys (such as waspaloy and haynes 230) contain nearly 50% nickel, around 19% to 20% chromium, about 10% cobalt, and other elements like tungsten and molybdenum.
• Nickel-iron alloys (like permalloy) contain about 80% nickel with nearly 20% iron and small traces of other elements.

Elements Commonly Used in Metals

A number of elements are  used independently or alloyed with other elements to enhance a metal's mechanical properties.

Iron

Perhaps the most commonly-used element in metals is iron, which is known for its high strength, ductility, and magnetism. Iron is highly susceptible to corrosion.

Carbon

Although carbon is widely found in nature, it is not usually present in high quantities. Carbon only makes up approximately 0.025% of the Earth’s crust. It is, however, commonly found in many metals, mainly steels. Carbon increases hardness and strength when combined with iron. Although carbon enhances ductility in some steels, high amounts produce a steel with high wear resistance but low ductility. 

Chromium

Chromium is an essential element in stainless steel due to its corrosion-resistant properties. The addition of chromium to steel or stainless steel also increases hardness and strength of the metal at elevated temperatures.

Nickel

Nickel is highly ductile and corrosion resistant and is often used to enhance strength in high-temperature applications.

Manganese

Manganese is often used as an alloying agent in steel to enhance strength and toughness while maintaining ductility. Manganese also acts as a deoxidizer. (A deoxidizer displaces oxygen in the metal. This is important because oxygen may lead to impurities that weaken the metal and lead to defects in service.)

Silicon

The second most abundant element in Earth’s crust, silicon is often added to steel to enhance strength and hardness. It also acts as a deoxidizing agent during the manufacturing process. 

Aluminum

Aluminum is often used due to its lightweight, corrosion-resistant properties. Aluminum is highly malleable and an excellent conductor of thermal and electrical energy.

Copper 

Copper is best known for being highly malleable, lightweight, and resistant to corrosion. Copper is also the best conductor of electricity and is highly ductile.

Magnesium

Magnesium is lightweight, has a low density, and is a good conductor of electrical and thermal energy. 

Common Metal Alloys

Carbon steels are widely used because they are strong, workable, and cost effective. Brass (an alloy of copper and zinc) is common in plumbing fixtures. Copper is frequently used in electrical wiring and connectors due to its excellent conductivity.

Steel Alloys

Steel alloys come in various types and grades. They are widely used in bridges, buildings, railways, vehicle chassis, electrical components, and manufacturing tools and equipment.

Composition of Steel Alloys

Steel alloys are iron mixed with carbon and other elements to improve the metal's properties for specific uses. Depending on the alloying elements and their amounts, steel may have high strength, ductility, or resistance to wear and corrosion.

Types of Steel Alloys

A wide range of steel alloys are available on the market.

• Carbon steels are divided into low-, medium-, mild-, and high-carbon steels. Low-carbon steel is relatively low strength but highly malleable, whereas high-carbon steels are high in strength but often have lower ductility. 
• Stainless steel has a lower carbon content, but the addition of chromium gives it its characteristic corrosion-resistant properties.
• Tool steel is a high-strength steel used to make things like cutting tools to cut, drill, and machine other materials.

Aluminum Alloys

Aluminum and aluminum alloys are common in applications where either lightweight or corrosion resistance is a requirement. 

Composition of Aluminum Alloys

The most commonly-used elements in alloying aluminum are copper, magnesium, manganese, silicon, tin, nickel, and zinc

Types of Aluminum Alloys

Aluminum alloys are classified into two main subcategories based on their composition and method of processing: wrought alloys and cast alloys. 

Wrought alloys are designated by a four-digit numerical system — i.e., 1000 series through 8000 series alloys — and are shaped through a mechanical process such as rolling, forging, and extrusion. 

Cast aluminum alloys are formed by pouring molten aluminum into molds. They are also classified using a four-digit numerical system but with the format 1XX.X through 4XX.X.

Copper Alloys

Copper alloys are primarily copper, with the addition of other elements to provide and enhance desired mechanical properties.

Composition of Copper Alloys

Copper is alloyed with elements like zinc, silicon, tin, and nickel. Copper alloys are likewise categorized into wrought and cast alloys. 

Types of Copper Alloys

The main types of copper alloys are:

• Brass, which is made of copper and zinc. It is used in plumbing and pipe fittings, musical instruments, and decorative applications. 
• Bronze, which is made of copper and tin. It is found in bearings, sculptures, and decorative applications.
• Copper-nickel alloys are made of copper alloyed with nickel. They are typically used in marine applications, coins, and heat exchangers.
• Copper-silicon alloys are made by combining copper with silicon. They are often used in electrical components. 

How to Identify Metals

To work with metals safely and effectively, it's important to be able to identify them. Several methods enable material identification.

Visual Inspection

A visual inspection can tell a lot about a metal. Observing the metal’s color and surface finish gives important information regarding the identity of the metal.

Chemical Analysis

Chemical tests can identify metals. For example, copper reacts to the presence of nitric acid by producing a blue solution. 

Physical Testing

Magnetism tests can help identify metals. Non-ferrous metals don’t respond to magnets, whereas ferrous metals do. 

Density tests measure a metal’s weight in relation to its size, which helps distinguish between metals based on their specific densities. 

Hardness tests, like Brinell or Rockwell, compare a material’s hardness to known standards for identification.

Spectroscopy

Spectroscopy determines the type of metal with a high degree of accuracy and reliability. 

X-Ray Fluorescence (XRF)

X-ray fluorescence identifies the electrical composition of a material by analyzing the fluorescent X-rays it produces when exposed to X-ray radiation.

Optical Emission Spectroscopy (OES)

Optical emission spectroscopy excites atoms in a test sample, causing them to emit light or photons based on the composition of the material. 

Mass Spectrometry

Mass spectrometry ionizes the chemicals in a sample and groups the ions based on their mass and charge to determine the exact material composition.

Electron Microscopy

Electron spectrometry involves measuring the energy of electrons that are ejected from a material that has been exposed to radiation, either in the form of X-rays or ultraviolet light.

Uses of Metals and Their Alloys

Metals have specific attributes based on their composition, which makes them suitable for certain applications.

Construction and Infrastructure

Steel alloys are strong and cost effective, making them ideal for beams in bridges, buildings, and railways. Aluminum is also used in smaller structures like canopies and frames, where both strength and light weight are necessary.

Aerospace Industry

High strength and lightweight materials are critical in the aerospace industry. Titanium is often used in aerospace applications for this reason.

Electronics

Copper is known for its excellent thermal and electrical conductivity, making it ideal for electronics and electrical applications. It is a key material for producing wires and other electronic components.

Medical Devices

The unique demands of medical applications require materials that meet the safety and precision standards of the medical field. For example, stainless steel is commonly used for surgical instrumentation, implants, and dental devices due to its high strength and corrosion resistance. 

Titanium, with its lightweight and high strength, make it uniquely suited for bone and dental implants. 

Aluminum and aluminum alloys have long been the material of choice for braces due to their lightweight but high strength and structural rigidity. 

Factors That Impact Metal Properties

Various factors negatively impact metal properties. If not properly managed, these issues may lead to service failures, potentially causing injury, environmental damage, or loss of life.

Temperature

Processing and welding temperatures, as well as service temperatures, affect metal strength. Metals designed for high heat should be used in these situations.

Corrosion

Corrosion erodes materials over time. Some chemicals also accelerate the rate of corrosion, which may result in the loss of containment. The addition of chromium when forming stainless steel creates a material that will last much longer in environments where corrosion is a factor. 

Mechanical Stress

Mechanical stress like internal pressure on pipes or vessels sometimes leads to failure. A material with high strength and higher ductility like steel may be well suited for situations where internal pressure will be present.

Alloying Elements

The composition of the metal influences its properties. For example, unwanted elements like oxygen weaken the metal, decreasing its strength and potentially leading to failure. 

Challenges in Metal Composition

Producers of metals, those who process and work with metals, and even end users of metals face several challenges.

Contamination and Impurities

Unwanted elements accidentally introduced during metal manufacturing may reduce the metal's quality and performance, potentially leading to significant failures during use.

Consistency in Manufacturing

Differences in raw materials may lead to a high degree of inconsistency in composition, which may have an adverse effect on a material's capability to perform up to project specifications.

Regulatory Standards

Making sure materials meet demanding and stringent requirements is challenging. Environmental restrictions on mining which may make it more difficult and costly to obtain elements necessary to make certain alloys.

Testing and Certification Standards

Regulatory agencies provide guidelines and standards to ensure metals meet universal quality and performance expectations. These ensure metals function as intended in various applications.

International Standards

The International Organization for Standardization (ISO) was formed by a group of nations in response to an increasingly global marketplace. They decided that materials and products bought and sold in the global marketplace should meet a set of uniform standards, mutually agreed upon by the member nations.

The American Society for Testing and Materials (ASTM)

The American Society for Testing and Materials (ASTM), established in 1898, develops and publishes technical standards for a wide range of materials. The ASTM provides guidelines for testing methods and specifications to ensure consistent metal quality.

European Standards (EN)

The EN Eurocodes are similar to ISO standards but focus specifically on regulatory requirements for industrial and construction applications, including metals. They involve collaboration with European member countries to develop standards for the production, classification, and testing of metals to ensure consistent quality.

Environmental Impact

Metals are essential in many industries, requiring large-scale production to meet global demand. For this to be sustainable, it’s necessary to produce metals efficiently while minimizing environmental impact.

Recycling of Metals

Recycling metals is one of the most effective ways to meet global demand while reducing the environmental impact. It minimizes the need for landfill space and decreases the demand for new mining. It is possible to recycle, reprocess, and resell all types of metals without diminishing their strength and other key properties.

FAQ

What is metal composition, and why is it important?

Metal composition determines the key characteristics of the material. For example, steel with high carbon content is strong but not particularly ductile, whereas adding chromium to steel makes it corrosion resistant, like stainless steel.

What are the main types of metals and their compositions?

The main way to categorize metals is by ferrous and non-ferrous. Ferrous metals contain iron, such as in the case of steel and stainless steel. Non-ferrous metals (like copper, aluminum, and alloys such as bronze and brass) do not contain iron.

How do alloying elements impact metal properties?

Alloying elements may significantly enhance metal properties. For instance, adding zinc to copper creates brass, which is known for its aesthetics and corrosion resistance.

Chromium in steel reduces carbon content and improves corrosion resistance, such as in the case of stainless steel.

Adding nickel increases resistance to oxidation at high temperatures.

 

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