Mailing List

Subscribe for occasional updates:

Engineering materials refers to the group of materials that are used in the construction of manmade structures and components. The primary function of an engineering material is to withstand applied loading without breaking and without exhibiting excessive deflection. The major classifications of engineering materials include metals, polymers, ceramics, and composites. The important characteristics of the materials within each of these classes are discussed on this page, and tables of material properties are also provided.

Contents

Metals

Metals are the most commonly used class of engineering material. Metal alloys are especially common, and they are formed by combining a metal with one or more other metallic and/or non-metallic materials. The combination usually occurs through a process of melting, mixing, and cooling. The goal of alloying is to improve the properties of the base material in some desirable way.

Metal alloy compositions are described in terms of the percentages of the various elements in the alloy, where the percentages are measured by weight.

Ferrous Alloys

Ferrous alloys have iron as the base element. These alloys and include steels and cast irons. Ferrous alloys are the most common metal alloys in use due to the abundance of iron, ease of production, and high versatility of the material. The biggest disadvantage of many ferrous alloys is low corrosion resistance.

Carbon is an important alloying element in all ferrous alloys. In general, higher levels of carbon increase strength and hardness, and decrease ductility and weldability.

Carbon Steel

Carbon steels are basically just mixtures of iron and carbon. They may contain small amounts of other elements, but carbon is the primary alloying ingredient. The effect of adding carbon is an increase in strength and hardness.

Most carbon steels are plain carbon steels, of which there are several types.

Low-Carbon Steel

Low-carbon steel has less than about 0.30% carbon. It is characterized by low strength but high ductility. Some strengthening can be achieved through cold working, but it does not respond well to heat treatment. Low-carbon steel is very weldable and is inexpensive to produce. Common uses for low-carbon steel include wire, structural shapes, machine parts, and sheet metal.

Medium-Carbon Steel

Medium-carbon steel contains between about 0.30% to 0.70% carbon. It can be heat treated to increase strength, especially with the higher carbon contents. Medium-carbon steel is frequently used for axles, gears, shafts, and machine parts.

High-Carbon Steel

High-carbon steel contains between about 0.70% to 1.40% carbon. It has high strength but low ductility. Common uses include drills, cutting tools, knives, and springs.

Carbon Steel Materials Table

The table below provides representative mechanical properties for several common carbon steels. (Note 1)

Material Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
AISI 1020 Hot Rolled 32 50 25 29e6 0.283 0.32
Cold Worked 60 70 5
Stress Relieved 50 65 10
Annealed 28 48 30
Normalized 34 55 22
AISI 1045 Hot Rolled 45 75 15 29e6 0.283 0.32
Cold Worked 80 90 5
Stress Relieved 70 80 8
Annealed 35 65 20
Normalized 48 75 15
ASTM A36 36 58 21 29e6 0.283 0.3
ASTM A516 Grade 70 38 70 17 29e6 0.283 0.3
NOTE : See our materials database for data conforming to specific material specifications.

Low-Alloy Steel

Low-alloy steels, also commonly called alloy steels, contain less than about 8% total alloying ingredients. Low-alloy steels are typically stronger than carbon steels and have better corrosion resistance.

Some low-alloy steels are designated as high-strength low-alloy (HSLA) steels. What sets HSLA steels apart from other low-alloy steels is that they are designed to achieve specific mechanical properties rather than to meet a specific chemical composition.

The table below provides representative mechanical properties for several common alloy steels. (Note 1)

Material Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
AISI 4130 Hot Rolled 70 90 20 29e6 0.283 0.32
Stress Relieved 85 105 10
Annealed 55 75 30
Normalized 60 90 20
AISI 4140 Hot Rolled 90 120 15 29.7e6 0.283 0.32
Stress Relieved 100 120 10
Annealed 60 80 25
Normalized 90 120 20
ASTM A242 46 67 18 30e6 0.282 0.3
ASTM A302 Grade A 45 75 15 29e6 0.282 0.29
Grade C 50 80 17
ASTM A514 Quenched & Tempered 100 110 18 29e6 0.283 0.3
ASTM A517 Grade F 100 115 16 29e6 0.280 0.29
ASTM A533 Class 1 50 80 18 29e6 0.282 0.29
Class 2 70 90 16
Class 3 83 100 16
ASTM A572 Grade 50 50 65 18 30e6 0.283 0.3
ASTM A588 50 70 18 29.7e6 0.280 0.28
ASTM A633 Grade E 55 75 18 29.7e6 0.280 0.28
ASTM A656 Grade 50 50 60 20 29e6 0.282 0.29
Grade 60 60 70 17
Grade 70 70 80 14
Grade 80 80 90 12
Grade 100 100 110 12
ASTM A710 Grade A 80 85 20 29.7e6 0.280 0.3
HY-80 80 --- 18 29.7e6 0.280 0.3
HY-100 100 --- 16 29.7e6 0.284 0.3
NOTE : See our materials database for data conforming to specific material specifications.

Tool Steel

Tool steels are primarily used to make tooling for use in manufacturing, for example cutting tools, drill bits, punches, dies, and chisels. Alloying elements are typically chosen to optimize hardness, wear resistance, and toughness.


Stainless Steel

Stainless steels have good corrosion resistance, mostly due to the addition of chromium as an alloying ingredient. Stainless steels have a chromium composition of at least 11%. Passivation occurs with chromium content at or above 12%, in which case a protective inert film of chromic oxide forms over the material and prevents oxidation. The corrosion resistance of stainless steel is a result of this passivation.

The table below shows the typical compositions of stainless steels:

Element Austenitic Ferritic Martensitic
Carbon 0.03 - 0.25% 0.08 - 0.20% 0.15 - 1.2%
Chromium 16 - 26% 11 - 27% 11.5 - 18%
Nickel 3.5 - 22% --- ---
Manganese 2% 1 - 1.5% 1%
Silicon 1 - 2% 1% 1%
NOTE : Table adapted from Lindeburg.
Austenitic Stainless Steel

Austenitic stainless steel is the most common form of stainless steel. It has the highest general corrosion resistance among stainless steels. It is also the most weldable of the stainless steels due to its low carbon content. It can only be strengthened through cold work. Austenitic stainless steels are generally more expensive than other stainless steels due to nickel content. Austenitic stainless steels are not magnetic, although ferritic and martensitic stainless steels are. Common applications include fasteners, pressure vessels, and piping.

Ferritic Stainless Steel

Ferritic stainless steel has high chromium content and medium carbon content. It has good corrosion resistance rather than high strength. It generally cannot be strengthened through heat treatment, and can only be strengthened via cold work.

Martensitic Stainless Steel

Martensitic stainless steel has high carbon content (up to 2%) and low chromium content. This higher carbon content is the primary difference between ferritic and martensitic stainless steels. Due to the high carbon content, it is difficult to weld. It can be strengthened through heat treatment. Common applications include cutlery and surgical instruments.

Duplex Stainless Steel

Duplex stainless steel contains both austenitic and ferritic phases. It can have up to twice the strength of austenitic stainless steel. It also has a high toughness, corrosion resistance, and wear resistance. Duplex stainless steel is generally as weldabe as austenitic, but it has a temperature limit.

Precipitation-Hardenable Stainless Steel

Precipitation-hardenable stainless steel can be strengthened through precipitation hardening, which is an age hardening process. These materials have high strength as well as high resistance to corrosion and temperature.

Stainless Steel Materials Table

The table below provides representative mechanical properties for several common stainless steels. (Note 1)

Material Class Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
AISI 201 Austenitic Annealed 40 75 40 28e6 0.289 0.27
AISI 202 Austenitic Annealed 40 75 40 28e6 0.289 0.27
AISI 302 Austenitic Annealed 30 75 40 28e6 0.289 0.27
AISI 304 Austenitic Annealed 30 75 40 28e6 0.289 0.29
AISI 304L Austenitic Annealed 25 70 40 28e6 0.289 0.28
AISI 316 Austenitic Annealed 30 75 40 28e6 0.289 0.26
AISI 316L Austenitic Annealed 25 70 40 28e6 0.289 0.26
AISI 405 Ferritic 25 60 20 29e6 0.282 0.28
AISI 410 Martensitic Annealed 40 70 16 29e6 0.282 0.28
Quenched & Tempered 80 100 12
AISI 430 Ferritic 30 60 20 29e6 0.282 0.28
AISI 446 Ferritic Annealed 40 65 16 29e6 0.282 0.28
15-5PH Martensitic precipitation hardenable H900 170 190 10 28.5e6 0.283 0.27
H1025 145 155 12
H1150 105 135 16
17-4PH Martensitic precipitation hardenable H900 170 190 10 28.5e6 0.282 0.27
H1025 145 155 12
H1150 105 135 16
17-7PH Semiaustenitic precipitation hardenable TH1050 150 177 6 29e6 0.276 0.28
A-286 Austenitic precipitation hardenable 95 140 15 29.1e6 0.287 0.31
Alloy 2205 Duplex Austenitic-Ferritic 65 95 25 28.5e6 0.287 0.27
Ferrallium 255 Duplex Austenitic-Ferritic 80 110 15 28.5e6 0.287 0.27
NOTE : See our materials database for data conforming to specific material specifications.

Cast Iron

Cast iron is a ferrous alloy containing high levels of carbon, generally greater than 2%. The carbon present in the cast iron can take the form of graphite or carbide. Cast irons have a low melting temperature which makes them well suited to casting.

Gray Cast Iron

Gray cast iron is the most common type. The carbon is in the form of graphite flakes. Gray cast iron is a brittle material and its compressive strength is much higher than its tensile strength. The fracture surface of gray cast iron has a gray color, which is how it got its name.

Ductile Cast Iron (Nodular Cast Iron)

The addition of magnesium to gray cast iron improves the ductility of the material. The resulting material is called nodular cast iron because the magnesium causes the graphite flakes to form into spherical nodules. It is also called ductile cast iron. Nodular cast iron has good strength, ductility, and machinability. Common uses include crankshafts, gears, pump bodies, valves, and machine parts.

White Cast Iron

White cast iron has carbon in the form of carbide, which makes the material hard, brittle, and difficult to machine. White cast iron is primarily used for wear-resisting components as well as for the production of malleable cast iron.

Malleable Cast Iron

Malleable cast iron is produced by heat treating white cast iron. The heat treatment improves the ductility of the material while maintaining its high strength.

Cast Iron Materials Table

The table below provides representative mechanical properties for several common cast irons. (Note 1)

Material Class Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
ASTM A159 Gray Cast Iron G1800 --- 18 --- 9.6 - 14e6 0.264 0.26
G2500 --- 25 --- 12 - 15e6
G3000 --- 30 --- 13 - 16.4e6
G3500 --- 35 --- 14.5 - 17e6
G4000 --- 40 --- 16 - 20e6
ASTM A536 Ductile Cast Iron Grade 60-40-18 40 60 18 24.5e6 0.256 0.29
Grade 65-45-12 45 65 12 24.5e6 0.256 0.3
Grade 80-55-06 55 80 6 24.5e6 0.256 0.31
Grade 100-70-03 70 100 3 24.5e6 0.256 0.3
Grade 120-90-02 90 120 2 23.8e6 0.256 0.28
NOTE : See our materials database for data conforming to specific material specifications.



Aluminum Alloys

Pure aluminum is soft and weak, but it can be alloyed to increase strength. Pure aluminum has good corrosion resistance due to an oxide coating that forms over the material and prevents oxidation. Alloying the aluminum tends to reduce its corrosion resistance.

Aluminum is a widely used material, particularly in the aerospace industry, due to its light weight and corrosion resistance. Despite the fact that aluminum alloys are generally not as strong as steels, they nevertheless have a good strength-to-weight ratio.

Aluminum alloys are named according to a 4-digit number, where the first number indicates the major alloying element. A processing code follows the 4-digit number, which indicates the condition and treatment of the material.

Series Major Alloying Element Heat Treatale
1XXX None (commercially pure) No
2XXX Copper Yes
3XXX Manganese No
4XXX Silicon No (mostly)
5XXX Magnesium No
6XXX Magnesium and Silicon Yes
7XXX Zinc Yes

Suffix Treatment
-F As fabricated
-O Annealed
-HX Cold worked (strain hardened)
-TX Solution heat treated, precipitation hardened

The 2000, 6000, and 7000 series aluminum alloys can all be heat treated, and therefore these can achieve the highest strengths. The other alloys can be strengthened through cold work.

The table below provides representative mechanical properties for several common aluminum alloys. (Note 1)

Material Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
Al 2014 T6, T651 59 67 7 10.5 0.101 0.33
Al 2024 T4 40 62 10 10.5 0.1 0.33
Al 5052 H32 23 38 9 10.1 0.097 0.33
Al 5083 H116, H321 31 44 10 10.3 0.096 0.33
H32 31 56 12
Al 6061 T4 16 26 16 9.9 0.098 0.33
T6 35 38 8
Al 7075 T6, T651 68 78 6 10.3 0.101 0.33
NOTE : See our materials database for data conforming to specific material specifications.

Nickel Alloys

Nickel alloys have high temperature and corrosion resistance. Common alloying ingredients include copper, chromium, and iron. Common nickel alloys include Monel, K-Monel, Inconel, and Hastelloy.

The table below provides representative mechanical properties for several common nickel alloys. (Note 1)

Material Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
Hastelloy C-276 Solution annealed 41 100 40 29.8 0.321 0.28
Inconel 625 Grade 1 55 110 30 29.8 0.305 0.28
Grade 2 40 100 30
Inconel 686 Grade 1 85 120 20 29.8 0.315 0.28
Grade 2 125 135 20
Grade 3 150 160 20
Inconel 718 Solution annealed & aged 120 150 20 29.4 0.297 0.29
Solution heat treated 150 180 10
Inconel 725 Solution annealed 40 75 45 29.6 0.3 0.31
Solution annealed & aged 120 150 20
Monel 400 Annealed 25 70 35 26 0.319 0.32
Hot worked 40 75 30
Cold worked, stress relieved 50 80 20
Monel K-500 Annealed & aged 85 130 20 26 0.306 0.32
Cold worked & aged 100 140 15
NOTE : See our materials database for data conforming to specific material specifications.

Copper Alloys

Copper alloys are generally characterized as being electrically conductivity, having good corrosion resistance, and being relatively easy to form and cast. While they are a useful engineering material, copper alloys are also very attractive and are commonly used in decorative applications.

Copper alloys primarily consist of brasses and bronzes. Zinc is the major alloying ingredient in brass. Tin is a major alloying element in most bronzes. Bronzes may also contain aluminum, nickel, zinc, silicon, and other elements. The bronzes are typically stronger than the brasses while still maintaining good corrosion resistance.

The aluminum bronze alloys are very hard and have good wearing properties, and so are commonly used in bearing applications. The beryllium copper alloys have good strength and fatigue properties, and good wear resistance when lubricated properly. Beryllium copper is commonly used for springs, bearings, and bushings.

The table below provides representative mechanical properties for several common copper alloys. (Note 1)

Material Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
70/30 Copper-Nickel Annealed 18 45 30 21.8 0.323 0.3
Cold worked 50 65 10
90/10 Copper-Nickel Annealed 15 38 30 20.3 0.323 0.3
Cold worked 30 50 15
Aluminum Bronze 32 85 12 15.5 0.269 0.316
Beryllium Copper Solution heat treated 75 85 8 18.5 0.298 0.27
Precipitation heat treated 140 165 3
Nickel Aluminum Bronze 632 Annealed 34 90 10 16.7 0.274 0.32
Quench hardened 50 90 15
NOTE : See our materials database for data conforming to specific material specifications.

Titanium Alloys

Titanium alloys are light, strong, and have high corrosion resistance. Their density is much lower than steel, and their strength-to-weight ratio is excellent. For this reason, titanium alloys are used fairly commonly, especially in the aerospace industry. One primary downside of titanium alloys is the high cost.

There are three categories of titanium alloys: alpha alloys, beta alloys, and alpha-beta alloys. Alpha alloys do not respond to heat treatment and are instead strengthened through solid-solution strengthening processes. The beta and alpha-beta alloys can be strengthened by heat treatment, primarily through precipitation hardening.

Titanium alloys are identified using the percentages of alloying elements, for example Ti-6Al-4V.

The table below provides representative mechanical properties for several common titanium alloys. (Note 1)

Material Condition Yield
Strength [ksi]
Ultimate
Strength [ksi]
Elongation
%
Elastic
Modulus [psi]
Density
[lb/in3]
Poisson's
Ratio
Commercially Pure Grade 2 40 50 20 14.8 0.163 0.34
Ti-5Al-2.5Sn Annealed 110 115 10 15.5 0.162 0.31
Ti-6Al-4V Grade 5 120 130 10 16 0.16 0.31
Ti-6Al-4V, ELI Grade 23 110 120 10 16.5 0.16 0.31
Ti-5-1-1-1 Grade 32 85 100 10 16 0.16 0.31
NOTE : See our materials database for data conforming to specific material specifications.




Polymers

Polymers are materials that consist of molecules formed by long chains of repeating units. They may be natural or synthetic. Many useful engineering materials are polymers, such as plastics, rubbers, fibers, adhesives, and coatings. Polymers are classified as thermoplastic polymers, thermosetting polymers (thermosets), and elastomers.

Thermoplastic Polymers

The classification of thermoplastics and thermosets is based on their response to heat. If heat is applied to a thermoplastic, it will soften and melt. Once it is cooled, it will return to solid form. Thermoplastics do not experience any chemical change through repeated heating and cooling (unless the temperature is high enough to break the molecular bonds). They are therefore very well suited to injection molding.

Thermosetting Polymers

Thermosets are typically heated during initial processing, after which they become permanently hard. Thermosets will not melt upon reheating. If the applied heat becomes extreme however, the thermoset will degrade due to breaking of the molecular bonds. Thermosets typically have greater hardness and strength than thermoplastics. They also typically have better dimensional stability than thermoplastics, meaning that they are better at maintaining their original dimensions when subjected to temperature and moisture changes.

Elastomers

Elastomers are highly elastic polymers with mechanical properties similar to rubber. Elastomers are commonly used for seals, adhesives, hoses, belts, and other flexible parts. The strength and stiffness of rubber can be increased through a process called vulcanization, which involves adding sulfur and subjecting the material to high temperature and pressure. This process causes cross-links to form between the polymer chains.


Ceramics

Ceramics are solid compounds that may consist of metallic or nonmetallic elements. The primary classifications of ceramics include glasses, cements, clay products, refractories, and abrasives.

Ceramics generally have excellent corrosion and wear resistance, high melting temperature, high stiffness, and low electrical and thermal conductivity. Ceramics are also very brittle materials.

Glass

Glasses are common materials and are seen in applications including windows, lenses, and containers. Glasses are amorphous, whereas the other ceramics are mainly crystalline. Primary advantages of glasses include transparency and ease of fabrication. The base element of most glasses is silica, and other components can be added to modify its properties. Common processes used to form glass include:

  • heating until melting, then pouring into molds to cast into useful shapes
  • heating until soft, then rolling
  • heating until soft, then blowing into desired shapes

Cements

Cements are materials that, after mixing with water, form a paste that then hardens. Because of this characteristic, cements can be formed into useful shapes while in paste form before they harden into rigid structures. Plaster of paris is one common cement. The most common cement is called Portland cement, which is made by mixing clay and limestone and then firing at high temperature. Portland cement is used to form concrete, which is made by mixing it with sand, gravel, and water. It can also be mixed with sand and water to form mortar. Like other ceramics, cements are weak in tension but strong in compression. Cement is very inexpensive to produce, and it used widely in the construction of buildings, bridges, and other large structures.

Clay Products

Clay is a very common ceramic material. It can be mixed with water, shaped, and then hardened through firing at high temperature. The two primary classifications of clay products include structural clay products and whitewares. Structural clay products see applications including bricks, tiles, and piping. Whitewares see applications including pottery and plumbing fixtures.

Refractories

Refractory ceramics can withstand high temperatures and extreme environments. They can also provide thermal insulation. Brick is the most common refractory ceramic.

Abrasives

Abrasive ceramics are hard materials that are used to cut, grind, and wear away other softer materials. Typical properties of abrasives include high hardness, wear resistance, and temperature resistance. Abrasives can either be bonded to a surface (e.g. grinding wheels and sand paper), or can be used as loose grains (e.g. sand blasting). Common abrasives include cemented carbide, silicon carbide, tungsten carbide, aluminum oxide, and silica sand. Diamond is also an excellent abrasive, but it is expensive.


Composites

A composite material is a material in which one or more mutually insoluble materials are mixed or bonded together. The primary classes of composites are particulate composites, fibrous composites, and laminated composites.

Particulate Composites

Particulate composites are created by adding particles of one material to a matrix (the filler material). The particles will typically account for less than 15% of the total material volume. The particles are added to improve upon some shortcoming of the matrix material.

Fibrous Composites

A fibrous composite is a material in which fibers of one material are embedded within a matrix. The fibers carry most of the stress, and the matrix serves to hold the fibers in place and to transmit stress between the fibers. The fibers can be short and randomly oriented, or they can be long and continuous.

Laminated Composites

Laminated composites are created by combining layers of composite materials. The layers will typically differ in the orientation of the fibers, or they will differ in the material itself. Sandwich materials are common, in which a lightweight material (such as foam or a honeycomb) will be placed in between layers of a strong, stiff material.


Mailing List

Subscribe to receive occasional updates on the latest improvements:


Notes


Note 1: Material Property Data

The material property data provided are intended to be representative of the material described. The provided values tend toward the conservative end of the spectrum and could be used as baseline design values for preliminary design. However, these values do not conform to any particular specification, and so they should not be used in final design without first consulting with the appropriate material specifications. The data are provided "as is" without warranty of any kind, either expressed or implied. MechaniCalc, Inc. shall not be liable for any damages arising from the use of this data.


References

  1. Callister, William D., "Materials Science and Engineering: An Introduction," 9th Edition
  2. Dowling, Norman E., "Mechanical Behavior of Materials: Engineering Methods for Deformation, Fracture, and Fatigue," 4th Edition
  3. Lindeburg, Michael R., "Mechanical Engineering Reference Manual for the PE Exam," 13th Ed.
  4. Machinery's Handbook, 30th Edition, Industrial Press Inc.
  5. MMPDS-04, "Metallic Materials Properties Development and Standardization (MMPDS)," April 2008