Methods of strengthen crystalline materials against plastic , Other Engineering

Assignment Help:

Q. Describe the four main methods of strengthen crystalline materials against plastic yield.

Ans. (1) Work Hardening: Strain hardening or work hardening is a phenomenon which results in an increase in hardness and strength of a metal subjected to plastic deformation at temperatures lower than the Recrystallization range.

      The increase in the stress required to cause slip because of previous plastic deformation is known as work hardening.

         (2) Grain Refinement: Grain boundaries are region where atoms are at higher energy level and also where atomic orientation changes. Dislocation cannot glide past the grain boundaries easily. Hence, if there are more grain boundaries, there is more resistance to the movement of dislocations and hence an increase in strength. If there are more grains in a given amount of material, i.e., if the size of grains or crystals is smaller, there will is more grain boundaries compared to the case when the grains are larger. Hence, obviously the material with smaller grains or more grain boundaries will be stronger. Any process which tends to make the grains smaller will increase the strength of the material. This is the mechanism of strengthening by grain refinement.

        (3) Solid-Solution Strengthening: Another technique to strengthen and harden metals is alloying with impurity atoms that go into either substitution or interstitial solid solution. Accordingly, it is called solid-solution strengthening.

          Solid solution strengthen distorts the lattice, offers resistance to dislocation movement. Which is greater with interstitial elements which cause asymmetric lattice distortion e.g., carbon in steel.

         Due to the difference in atomic, lattice distortion is produced when one element is added to the other. Smaller atoms will produce a local tensile stress field and larger solute atoms will produce a local tensile stress field and larger solute atoms will produce a local compressive field in the crystal. In both the cases, the stress field of a moving dislocation interacts with the stress field of the solute atom. This increase the stress required to move the dislocation through crystal.

         (4) Dispersion Hardening: The resistance to motion of dislocation, in this strengthening mechanism, is increased by introducing finely divided hard particles of second phase in the soft matrix.

          The increase in hardness and tensile strength is due to the interaction of the stress field around the particles with the stress field around the particles with the stress field of a moving distortion and also due to physical obstruction by the hard particles to the moving dislocation. The increase in yield strength due to very hard and inert particles is given by the relation.

                                τ=C b/l


Related Discussions:- Methods of strengthen crystalline materials against plastic

Principles of sprinkler systems-fire safety engineering, Principles of Spri...

Principles of Sprinkler Systems-Fire safety Engineering Sprinkler systems may be installed in a building to achieve a number of different objectives.  Very often the primary r

Servicing of chemical de-icing systems, SERVICING OF CHEMICAL DE-ICING SYST...

SERVICING OF CHEMICAL DE-ICING SYSTEMS: It is essential for the correct operation of the ice protection system that servicing is carried out on a regular basis.  The fluids use

Analog digital converter , Analog digital converter  Analog digital con...

Analog digital converter  Analog digital converter digitises the conditioned signal and presents it in a digital form, which is more convenient for long distance transmission,

Heat transfer, A 2-m long section of a 3-mm in diamter wire is maintained a...

A 2-m long section of a 3-mm in diamter wire is maintained at a constant surface temperature of 370C. The wire is subject to a cross-flow of air at 30C at 6 m/s Determine the rate

Nicol Prism., Explain the construction of nicol prism and its function.

Explain the construction of nicol prism and its function.

Homework, Please explain how risk is taken into account for a financial ins...

Please explain how risk is taken into account for a financial instrument

Java, I''m trying to figure out how to use a for and while loop to: print e...

I''m trying to figure out how to use a for and while loop to: print each word found in 4 columns across the output page, in the order they were found. This means you must print the

Non-coplaner, ''If a non-coplaner force system is acted upon by equal and o...

''If a non-coplaner force system is acted upon by equal and opposite forces,it must be in equilibrium''.State this statement is true or false.Please,give me a reason.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd