I am currently enrolled for mechanical engineering in Australia. It's fascinating that most of the topics from my course are available by you guys!! Really appreciating. :D
Dear Prof. I really appreciate the way of your teaching. I am Pursuing PhD in Mechanical and major contents are aligned towards my study. Thanks again for the in depth explanation.
Is there any video or explanation how to apply this in practice? I assume multiple annealing after high plastic deformation, or forging-annealing repeated process? Also what determens how much new grains will start to grow from single grain during recrystalisation? Would be great to add particless for grain boundaries curving , but with opposite charge like foreign single grains to act as repeling force, it would be much harder to slip.
Small grains will increase creep rate through two mechanisms which do not involve dislocation motions. One is the diffusion of vacancies from boundary oriented perpendicular to stress axis to boundary parallel to stress axis. This is stress assisted diffusion. And the diffusion distance depends upon the grain size. So smaller the grains size, shorter the diffusion distance and so more diffusion and associated creep. The second is grain boundary sliding. Smaller grains provide more boundary area to slide on thus increasing creep by grain boundary sliding
@@introductiontomaterialsscience sir when you talk reasoning about strees assisted diffusion then why single fine crystals have high creep resistance they also will have vacancy assisted diffusion and as the grain size is small I The diffusion should be more according to that logic
@@aravindkumar6631 Single crystals do not have small grain size. The entire sample is a single grain, so the grain size is as large as the sample itself. There is nothing like single fine crystals.
sir, can you please suggest to me the best method to find the avg grain size of the rolled specimen when I measure along the rolling direction the grain size is more and when I measure along the transverse direction grain size is less. As people say rolling increases the grain sir which one we have to use either rolling direction or transverse direction?
Both the increase in strength and ductility is observed experimentally. Increase in strength is explained theoretically by the obstruction to the dislocation motion. I am not aware of any simple theoretical explanation for the increase in ductility.
Usually, strain field induced by interstitial solid solution is much more than that introduced by a substitutional solid solution. This is the reason by the interstitial solid solubility of C in Fe is so limited.Thus a small amount of C causes more hardening than similar or even more amount of Cr.
sir, I am working on Al-Li 8090 alloy, I found the higher strength on T3 temper which has coarse grain after annealing the grain are fine but with lower strength can you please explain this? 6:08!
Manish Negi larger the grain size more will be th ductility as the obstacles in dislocation motion is less and it is easy to deform the material plastically
@@AForAyush25 do you have any reference book ? I read quora ans but some of them said reverse of this...So I am in so much confusion about this thing...
The plane defined by the dislocation and its Burgers vector is called its slip plane. Thus the dislocation lies on the slip plane. To male it glide along the slip plane we need to apply a shear stress larger than a critical value called the critical resolved shear stress.
I am currently enrolled for mechanical engineering in Australia. It's fascinating that most of the topics from my course are available by you guys!! Really appreciating. :D
Sir, I am AMIE in Mech Engg but today I understood this theory in deep. Thanks a lot. Vidwan sarvatra poojyate
The best Tutor!!! Dr. RAJESH PRASAD
Dear Prof. I really appreciate the way of your teaching. I am Pursuing PhD in Mechanical and major contents are aligned towards my study. Thanks again for the in depth explanation.
Is there any video or explanation how to apply this in practice? I assume multiple annealing after high plastic deformation, or forging-annealing repeated process? Also what determens how much new grains will start to grow from single grain during recrystalisation? Would be great to add particless for grain boundaries curving , but with opposite charge like foreign single grains to act as repeling force, it would be much harder to slip.
Sir we want more NPTEL lectures from you.
Please make lectures on others topics as well.
Please sir.
thanks, simpe and effective
Sir, please take a video about solidification in detail
Hats off to your efforts Sir ☺️
Informative...nice lecture
Great video, thanks you so much
Sir can u please tell that
a) how grain size affect thermal conductivity??
b) how grain size affect fatigue strength ??
Very good explanation
very helpful video. I have a question though. How come small grains increase creep rates?
Small grains will increase creep rate through two mechanisms which do not involve dislocation motions.
One is the diffusion of vacancies from boundary oriented perpendicular to stress axis to boundary parallel to stress axis. This is stress assisted diffusion. And the diffusion distance depends upon the grain size. So smaller the grains size, shorter the diffusion distance and so more diffusion and associated creep.
The second is grain boundary sliding. Smaller grains provide more boundary area to slide on thus increasing creep by grain boundary sliding
@@introductiontomaterialsscience sir when you talk reasoning about strees assisted diffusion then why single fine crystals have high creep resistance they also will have vacancy assisted diffusion and as the grain size is small I
The diffusion should be more according to that logic
@@aravindkumar6631 Single crystals do not have small grain size. The entire sample is a single grain, so the grain size is as large as the sample itself.
There is nothing like single fine crystals.
Excellent
Thankyou sir
Great thanks Sir
sir, can you please suggest to me the best method to find the avg grain size of the rolled specimen when I measure along the rolling direction the grain size is more and when I measure along the transverse direction grain size is less. As people say rolling increases the grain sir which one we have to use either rolling direction or transverse direction?
Did you get any reply to this query...if you can share your findings, I will be obliged....looking forward
ur gr8 sir
why do they say grain refinement is way to achive both high strength and ductility
Both the increase in strength and ductility is observed experimentally. Increase in strength is explained theoretically by the obstruction to the dislocation motion. I am not aware of any simple theoretical explanation for the increase in ductility.
I assume the last equation should be L / ( M x ( N - 1 )) ?
for steels carbon as interstitial inclusion is generally stronger than chromium as substitution solid solution, why?
even if the strain field generated by chromium would be higher!
Usually, strain field induced by interstitial solid solution is much more than that introduced by a substitutional solid solution. This is the reason by the interstitial solid solubility of C in Fe is so limited.Thus a small amount of C causes more hardening than similar or even more amount of Cr.
❤❤❤
sir, I am working on Al-Li 8090 alloy, I found the higher strength on T3 temper which has coarse grain after annealing the grain are fine but with lower strength can you please explain this? 6:08!
This is interesting! I have no explanation.
Sit please clarify me that here the grain diameter we talking about is Prior Austenite grain Boundary Or ferrite size ?
What is described here is a general phenomenon applicable to all materials. For mild steels, you can take the ferrite size as the grain size.
@@introductiontomaterialsscience thank you proff.
sir what is the effect of grain size on ductility...plz explain it
Manish Negi larger the grain size more will be th ductility as the obstacles in dislocation motion is less and it is easy to deform the material plastically
@@AForAyush25 do you have any reference book ? I read quora ans but some of them said reverse of this...So I am in so much confusion about this thing...
Strong materials are less ductile. So, if you start reducing grain size you will also reduce ductility.
The more finer the grains the more ductile material.
Sir, how can we say that dislocation will be at the slip plane and on what basis we can say that the dislocation will slide on the slip plane?
The plane defined by the dislocation and its Burgers vector is called its slip plane. Thus the dislocation lies on the slip plane. To male it glide along the slip plane we need to apply a shear stress larger than a critical value called the critical resolved shear stress.
@@introductiontomaterialsscience Got it Sir. Thanks for your early response
Sir at 12:45 you told that there are N intercepts. But if there are N intersections then there should be N-1 intercepts. Isn't that correct
Well, at both ends we count only half intercepts thus giving N intercepts for N intersections.
yaar simple language me kyu nhi btate sir....sab upper se nikal gya