As soon as the model is shown, one can easily understand how to connect the two seemingly unrelated topics, namely 1. Small angle tilt boundary 2. Parallel edge dislocation It was like something was right in front of my eyes and yet I couldn't notice it.
Hi Professor Rajesh Prasad, please, where I can buy this model of a low angle symmetric tilt boundary that appears in 3:23 minutes of this video. Thanks. Congratulations for this videos...
Dear Sir, how can we say that distance between consecutive dislocations from opposite sides are half that of the distance in one side? Isn't the better approach is to define the denomoninator term seperately, say, 'h' which is defined as the distance between consecutive dislocations on the one side.
Every dislocation has a core where the atoms are highly disturbed from their equilibrium position. This is something which is not captured in the models which I have used. The radius of the core is equal to a few interatomic spacing. Let this radius be r. Now the spacing of dislocations in the boundary plane is h. According to the formula derived for h one can see that h decreases as theta increases. If h becomes equal to 2r then the cores of the neighbouring dislocations will start to overlap and a model in terms of individual dislocations will break down. Thus the model is true only for low-angle symmetric tilt boundary. According to the book "Introduction to Dislocations" by D. Hull and D.J. Bacon the core radius can be taken to be between b and 4b (p69, 5th. Edn.). If we use h=2b corresponding to to r=b in the formula we get theta =14 Degrees. For r=4b, theta comes out to be less than 4 Degree.
Atoms at the grain boundary are at a higher energy level, due to broken and distorted bonds. Thus to reduce its energy, the metal gets rid of these higher energy atoms at a faster rate.
Sir, the rotation of axis should be parallel to have tilt boundary but when you are explaining the rotation of axis is horizontal that means it is perpendicular , I didn't got the clarity sir.
@@introductiontomaterialsscience sir if rotation of axis is horizontal than it will be perpendicular to the boundary.. How can we say it as tilt boundary
It is not 2b but 2d. The distance between successive dislocations is designated as d. But the half planes of these come from different crystals. To remain in the same crystal we take alternate dislocations. Thus AB becomes 2d.
As soon as the model is shown, one can easily understand how to connect the two seemingly unrelated topics, namely
1. Small angle tilt boundary
2. Parallel edge dislocation
It was like something was right in front of my eyes and yet I couldn't notice it.
Thank you sir for helping the poor and needy students for free 🙏
Thanks thanks...... A lot,,
I have highly confused about the surface dislocations,,, but now it's totally fine clearrence..
😍 .....🙏🙏🙏🙏🙏🙏🙏🙏🙏
Hi Professor Rajesh Prasad, please, where I can buy this model of a low angle symmetric tilt boundary that appears in 3:23 minutes of this video. Thanks. Congratulations for this videos...
Build your own if you understand the concept or if you are a teacher then make your students to do it👍
excellent lecturrre
How to distinguish between tilt boundary and srew dislocation in real cystal.
in some books given for small angles tan theta can be taken as theta, but while doing problem which one should we take tan theta r only theta..
For angles less than 10 degrees it does not matter whether you use theta or tan (theta).
@@rajeshprasad101Thank you Sir..
Dear Sir, how can we say that distance between consecutive dislocations from opposite sides are half that of the distance in one side? Isn't the better approach is to define the denomoninator term seperately, say, 'h' which is defined as the distance between consecutive dislocations on the one side.
Sir, can't we say tilt boundary as a series of edge dislocation for symmetric large-angle also? If not then why?
Every dislocation has a core where the atoms are highly disturbed from their equilibrium position. This is something which is not captured in the models which I have used. The radius of the core is equal to a few interatomic spacing. Let this radius be r. Now the spacing of dislocations in the boundary plane is h. According to the formula derived for h one can see that h decreases as theta increases. If h becomes equal to 2r then the cores of the neighbouring dislocations will start to overlap and a model in terms of individual dislocations will break down. Thus the model is true only for low-angle symmetric tilt boundary.
According to the book "Introduction to Dislocations" by D. Hull and D.J. Bacon the core radius can be taken to be between b and 4b (p69, 5th. Edn.). If we use h=2b corresponding to to r=b in the formula we get theta =14 Degrees. For r=4b, theta comes out to be less than 4 Degree.
See
Woah!!! Easily exaplained sir.🙌🙌🙌🙌
Sir, why do chemical etchants first attack the grain boundary and not the crystal?
Atoms at the grain boundary are at a higher energy level, due to broken and distorted bonds. Thus to reduce its energy, the metal gets rid of these higher energy atoms at a faster rate.
@@introductiontomaterialsscience Thanks a lot sir for explanation.
Sir, the rotation of axis should be parallel to have tilt boundary but when you are explaining the rotation of axis is horizontal that means it is perpendicular , I didn't got the clarity sir.
The boundary is a vertical plane and the rotation axis is the horizontal line lying in that plane.
@@introductiontomaterialsscience sir if rotation of axis is horizontal than it will be perpendicular to the boundary.. How can we say it as tilt boundary
@@kaspashravani9019 Every vertical plane has a horizontal direction lying in the plane (the intersection of the vertical and the horizontal planes)
Sin or cos ??? b/2d
why is AB 2b？
It is not 2b but 2d. The distance between successive dislocations is designated as d. But the half planes of these come from different crystals. To remain in the same crystal we take alternate dislocations. Thus AB becomes 2d.
Aapko Hindi mein gyan dena chahiye sir.adhik chhatro ko sahayta milegi aur aapka channel kaa lokapriyata bhi badhega .
Dhanyvaad🙏🙏🙏🙏❤️❤️❤️