What Is Ductility?- Meaning & Factors that Affect

What is Ductility?

Ductility is a capacity of a material to deform permanently (e.g., stretch, bend, or spread) in response to stress. Most common steels, for example, are quite ductile and hence can accommodate local stress concentrations.

Brittle materials, such as glass, cannot accommodate concentrations of stress because they lack ductility, and therefore fracture easily. When a material specimen is stressed, it deforms elastically (see elasticity) at first; above a certain deformation, called the elastic limit, deformation becomes permanent.

In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stress before failure.

Ductility is an important consideration in engineering and manufacturing, defining a material’s suitability for certain manufacturing operations (such as cold working) and its capacity to absorb mechanical overload. Materials that are generally described as ductile include gold and copper.

Malleability, a similar mechanical property, is characterized by a material’s ability to deform plastically without failure under compressive stress. Historically, materials were considered malleable if they were amenable to forming by hammering or rolling. Lead is an example of a material that is relatively malleable but not ductile.

Examples

Most metals are good examples of ductile materials, including gold, silver, copper, erbium, terbium, samarium aluminum, and steel have high ductility. Examples of metals that are not very ductile include tungsten and high-carbon steel. Nonmetals are not generally ductile.

How to Measure Ductility

Ductility is the ability of a metal to deform without fracturing. Metals that can be formed or pressed into another shape without any fracturing are considered to be ductile. Metals that fracture are classified as brittle (essentially the opposite of ductile).

Ductility plays a major role in formability. Metals that are excessively brittle may not be able to be formed successfully. For example, if a piece of metal is stretched into a thin wire, it is imperative that it has some ductility.

If the metal is too brittle, it will fracture as soon as the metal begins to stretch. Ductility is also a major safety consideration for structural projects. Ductility allows structures to bend and deform to some extent without rupturing when placed under heavy loads.

Percent elongation and percentage reduction are two ways to measure ductility:

  • Percentage elongation measures the length that a metal deforms as a percentage of its original length, after it is pulled to failure during a tensile test.
  • Percent reduction measures the narrowest part of the cross-section of a metal specimen following a tensile test-induced rupture.

Ductility can be dependent on temperature, so the temperatures the metal will be subjected to in an application should be taken into account. Most metals have a ductile-brittle transition temperature chart which can assist.

Which Metals Are Ductile?

There are many ductile metals, including:

  • Aluminum
  • Brass
  • Copper
  • Low carbon steel
  • Gold
  • Silver
  • Tin
  • Lead

Metals that are considered brittle include cast iron, chromium, and tungsten. Examples of applications that require high ductility include metal cables, stampings, and structural beams.

Materials science

Gold is extremely ductile. It can be drawn into a monatomic wire, and then stretched more before it breaks.

Ductility is especially important in metalworking, as materials that crack, break or shatter under stress cannot be manipulated using metal-forming processes such as hammering, rolling, drawing, or extruding. Malleable materials can be formed cold using stamping or pressing, whereas brittle materials may be cast or thermoformed.

High degrees of ductility occur due to metallic bonds, which are found predominantly in metals; this leads to the common perception that metals are ductile in general. In metallic bonds, valence shell electrons are delocalized and shared between many atoms.

The delocalized electrons allow metal atoms to slide past one another without being subjected to strong repulsive forces that would cause other materials to shatter.

The ductility of steel varies depending on the alloying constituents. Increasing the levels of carbon decreases ductility. Many plastics and amorphous solids, such as Play-Doh, are also malleable. The most ductile metal is platinum and the most malleable metal is gold.

When highly stretched, such metals distort via formation, reorientation, and migration of dislocations and crystal twins without noticeable hardening.

Factors that Affect Ductility of Metals:

Ductility is affected by intrinsic factors like composition, grain size, cell structure, etc., as well as by external factors like hydrostatic pressure, temperature, plastic deformation already suffered, etc.

Some important observations about ductility are given below:

  1. Metals with FCC and BCC crystal structure show higher ductility at high temperatures compared to those with HCP crystal structure.
  2. Grain size has a significant influence on ductility. Many alloys show super-plastic behavior when the grain size is very small in the order of few microns.
  3. Steels with higher oxygen content show low ductility.
  4. In some alloy’s impurities even in very small percentages have a significant effect on ductility. The ductility of carbon steels containing sulfur impurity as small as 0.018%, drastically decreases ductility at around 1040°C. This can however be remedied if Mn content is high. In fact, the ratio Mn/S is the factor that can alter the ductility of carbon steels at 1040°C. With the value of this ratio at 2, the percent elongation is only 12-15% at 1040°C while with a ratio of 14 it is 110 percent.
  5. Temperature is a major factor that influences ductility and hence formability. In general, it increases ductility, however, ductility may decrease at certain temperatures due to phase transformation and microstructural changes brought about by an increase in temperature. The effect of temperature on the ductility of stainless steel. It has low ductility at 1050°C and a maximum at 1350°C. Therefore, it has a very narrow hot working range.
  6. Hydrostatic pressure increases ductility. This observation was first made by Bridgeman. In torsion tests, the length of the specimen decreases with an increase in torsion. If the specimen is subjected to axial compressive stress in the torsion test it shows higher ductility than when there is no axial stress. If tensile axial stress is applied the ductility decreases still further.

FAQs.

What is Ductility?

Ductility is a capacity of a material to deform permanently (e.g., stretch, bend, or spread) in response to stress. Most common steels, for example, are quite ductile and hence can accommodate local stress concentrations.

What is example of ductility?

Ductility is the physical property of a material associated with the ability to be hammered thin or stretched into wire without breaking. A ductile substance can be drawn into a wire. Examples: Most metals are good examples of ductile materials, including gold, silver, copper, erbium, terbium, and samarium.

What is meant by malleability and ductility?

A malleable material is one in which a thin sheet can be easily formed by hammering. Gold is the most malleable metal. Credit: Buzzle. In contrast, ductility is the ability of a solid material to deform under tensile stress.

Why ductility is a metal?

High degrees of ductility occur due to metallic bonds, which are found predominantly in metals; this leads to the common perception that metals are ductile in general. In metallic bonds, valence shell electrons are delocalized and shared between many atoms.

What is ductility short answer?

Ductility is the ability of a material to be drawn or plastically deformed without fracture. It is therefore an indication of how ‘soft’ or malleable the material is.

What is the use of ductility in everyday life?

Property of metalUse in everyday life 
Ductility In electrical wires, cable wires etc.
Malleability Aluminum wires 
Conduction of heat Cooking wares, microwave, electric press, straightening 
machine, electric belts
Conduction of electricity Bulb, tube light, lamp, refrigerator, television
Sonority Cymbals, doorbells

How do you increase your ductility?

The heating rate, dwell/ cooling rate can be adjusted to get the desired improvement in ductility. This method is referred to as annealing in steels. i study the deformation of magnesium alloy, i think refine the grain size is a good way to improve the ductility.

What is the process of ductility?

Ductility is the plastic deformation that occurs in metal as a result of such types of strain. The term “ductile” literally means that a metal substance is capable of being stretched into a thin wire without becoming weaker or more brittle in the process.

What is my ability and ductility?

The term ductility is the ability of a material to be drawn or plastically that is deformed without fracture. It is therefore said to be an indication of how ‘soft’ or malleable the material is. Still, there is the ductility of steels that varies depending on the types and levels of alloying elements present.

What are the factors affecting ductility?

Factors that Affect Ductility of Metals: Ductility is affected by intrinsic factors like composition, grain size, cell structure, etc., as well as by external factors like hydrostatic pressure, temperature, plastic deformation already suffered, etc.

Why does cold-working increase ductility?

During cold-working there is an increase in the number of dislocations in metal compared to its pre-cold-worked condition. The increase in the number of dislocations causes a metal’s yield and tensile strength to increase and its ductility to decrease.

What is the opposite of ductility?

In this sense brittle is the opposite of ductile or malleable. When stress is applied to brittle material and the material fails, there is often a loud snap.

What is ductility Why is it important?

Ductility allows structures to bend and deform to some extent without rupturing. High ductility is critical in applications such as metal cables and structural beams. Gold, silver, and platinum are ductile metals. So are most aluminum alloys.

What is displacement ductility?

The displacement ductility demand (μ∆) is defined as the ratio of the peak non-linear displacement to the yield displacement. The displacement ductility demand varies strongly between different considered ground motions but means values obtained from a large number of ground motions show clear tendencies.

Why is ductility important structure?

The ductility of building structures is to ensure that buildings have a certain energy dissipation capacity and deformation to avoid sudden brittle damage in earthquake and fierce wind.

Does hot working increase ductility?

Hot-working improves the engineering properties of the workpiece because it replaces the microstructure with one that has fine spherical-shaped grains. These grains increase the strength, ductility, and toughness of the material.

Why does cold decrease ductility?

In cold rolling, the grains become elongated in the rolling direction. This increases the strength through work hardening, but ductility decreases. The higher the % cold work (ie % reduction in thickness), the lower the ductility. Because the grains are elongated in one direction, they develop a preferred orientation.

How does ductility affect the strength of a tension member?

Reduction in ductility tends to reduce the strength of members. An increase in ductility tends to increase net section strength by allowing better plastic redistribution of stress concentration over the cross-section.

What is the relation between malleability and ductility?

The main difference between ductility and malleability is that ductility is the ability of a metal to be drawn into wires, while malleability is the ability of a metal to be beaten into sheets. Ductility involves tensile stress, while malleability involves compressive stress.

Is ductility intensive or extensive?

Examples of intensive properties of matter are color, conductivity, melting point, ductility, pressure, freezing point, density, boiling point, odor, luster, and hardness, among others. Examples of extensive properties of matter are mass, volume, weight, and length.