Hats off. Mind blowing professor. Never understood the reason of finer and coarser grains. Also never paid heed to how TTT diagram is created. Amazing.... Thank you.
16:15 In Fast Cooling temperature range is lower than Slow Cooling And for Fast Cooling due to low temperature range we will get Fine Grains and for Slow Cooling due to High temp range we will get Coarse Grains 20:00 In case of Quenching 22:20 we will get Glass or Amorphous Solid
Sir, there can be a cooling curve in between nose of green curve and red curve, which cuts the green line but doesn't cut the red line. What would be out come of such curve?
Sir you said that for faster cooling,the temperature range for which transformation occurs is lower. Does this mean that the difference of upper and lower temperature values is lower than that for slow cooling? Because by observing the TTT diagram,it seems the other way around.
It means that the start temperature for faster cooling is lower than that for the slow cooling. similar the end temperature for faster cooling is lower than that for slower cooling.
Thanks for the video. Can anyone help? I would like to find out how to find out what quenching time is needed to achieve bainite transformation (bainite hardening) in chromoly alloy steel 42CrMo4 (SAE 4140). For example when I use oil as quenching medium with constant 350°C and I then I dip chromoly workpiece with austenite temperature into it and I need to know for how long it should stay in the oil and if there is a max time that can not be exceeded.
16:20 You said that "On faster cooling, the temperature range over which the transformation happens is lower than in slower cooling."; but instead the temperature range increases in faster cooling. Like in the cooling lines you have drawn, the slower cooling line has a small temperature range(the vertical height) when compared to faster cooling. I am confused here. Please help!!
Sir since at temperature below and above the nose the transformation rate is small so shouldn't it be that the gap between start and finish curve along isotherm should be larger as compared to nose because larger the transformation rate less time it will take to transform
Sir here at 16:19 the two cooling curve u took was it for water or alloy?because if its liquid water then its pure substance and pure substance solidifies at fixed temperature,if its alloy then how we are able to superimposed an alloy curve to an pure substance's TTT diagram?
This example is of a pure liquid. When we say a pure liquid freezes at a fixed temperature, we mean the temperature at which solid and liquid are in thermodynamic equilibrium. Freezing will happen at this temperature only if the cooling rate is extremely slow to allow for equilibrium to be attained. At normal or faster cooling rates undercooling is possible, i.e., the liquid will remain as a metastable liquid even below the equilibrium freezing temperature. This liquid can thus solidify at a temperature below the equilibrium freezing temperature.
Think of casting. Sand casting gives relatively slower cooling rate than die casting. And then there are techniques called rapid quenching where one cools so fast that one gets amorphous or glassy phase.
I think this video lecture is the ultimate explanation of TTT diagram in my opinion! So detailed, elabroated, and thorough lecture. Thank you so much sir!
Sir, will you please explain under what conditions it is called fast cooling and slow cooling? And if we do water quenched aluminum composite what will be the effects on grains, will it developed finer grains?
Lets see it for iron...Water quenching of austenite is fast. So it will give martensite directly(fast cooling). Oil quench will give very fine pearalite,air cooling will give fine pearalite. Nd furnace cooling will give coarse pearalite.
Sir, thank you for your very nice explanation of TTT diagram, but i have a quesiton.. in this video, your diagram looks like CCT diagram, not TTT diagram because of the continuous cooling rate you draw... so.. isn't it a CCT diagram??
You have asked a serious question. And that points to subtle point regarding the difference between TTT and CCT. The diagram I have drawn is a TTT diagram. The CCT diagram does not have the lower part of C curve. So strictly speaking I should not draw a continuous cooling curve on these diagrams. I avoided discussion on CCT diagrams in these videos. So I did not go into these details and loosely drew continuous cooling curve on a TTT diagram, which in a strict sense is incorrect.
Sir we've already seen that for an alloy, transformation occur at a range of temp.(except for eutectic composition)...but in TTT diagram phase transformation start and finished at the same temp...HOW IS THIS POSSIBLE??
If two identical materials are cooled with same cooling rate but one is cooled from say 820 and the other from 790, transformation temp of former being higher ,will it have coarser grains?
Sir, I have a question. Why when you supercool the liquid, during the crystallization, does the temperature decrease? I think the temperature should be supposed to keep constant.
The distinction between crystal and glass is their atomic arrangement. In crystals the atoms are periodically arranged. Atomic arrangement in glass is disordered. The atomic arrangement of liquid is also disordered and in this sense, glass is compared to a liquid.
Hats off. Mind blowing professor. Never understood the reason of finer and coarser grains. Also never paid heed to how TTT diagram is created. Amazing.... Thank you.
this really helps me review basic metallurgy for my thesis. thank you, sir. respect.
Which Iit?
Your teaching method and your knowledge of the subject are remarkable Professor.
So interesting video Sir..... Different colour are attractive..... It's perfect method to teach student.....
Thats y he teaches in IIT D.
Mera bhi sapna tha IIT ..but kya kare NIT mila...ussi me khus hu😥
@@unpluggedamit3647 which nit
16:15
In Fast Cooling temperature range is lower than Slow Cooling
And for Fast Cooling due to low temperature range we will get Fine Grains and for Slow Cooling due to High temp range we will get Coarse Grains 20:00
In case of Quenching 22:20 we will get Glass or Amorphous Solid
I have a question. Why during the crystallization, does the temperature decrease? I think the temperature should be supposed to keep constant.
If only such teachers existed all around!!❤️
Sir, there can be a cooling curve in between nose of green curve and red curve, which cuts the green line but doesn't cut the red line. What would be out come of such curve?
This is the best explanation of TTT curve....
Thank you very much sir
Remarkable...crystal clear explanation..Thanks a lot Sir
Thanks for this amazing lecture sir. Very simple explanation with deep understanding.
Cleared all the ambiguity regarding T-T-T diagram in the most effective manner. Excellent piece of teaching. Thank you very much sir.
Very good video, would recommend 1.25 speed for viewing.
After Coarse Pearlite is formed then I quench it to room temperature what I will get?
It will remain coarse pearlite. Once austenite is transformed, no further transformation is expected.
Sir you said that for faster cooling,the temperature range for which transformation occurs is lower. Does this mean that the difference of upper and lower temperature values is lower than that for slow cooling? Because by observing the TTT diagram,it seems the other way around.
It means that the start temperature for faster cooling is lower than that for the slow cooling. similar the end temperature for faster cooling is lower than that for slower cooling.
@@rajeshprasad101 Thanks sir I got it.
Dear Sir, thanks for the lovely explanation. I have one question, can any liquid be transformed to Glass by Quenching?
Yes. If you cool a liquid fast enough there is no time for atoms to organise in crystalline structure. Thus it becomes glass.
@@introductiontomaterialsscience thank you Sir
Being speechless after watching this video.... awzm sir.
Excited to study what happened in the nxt lecture
beautifully explained the ttt diagram concept
Thanks sir for your easy explanations
Thanks for the video. Can anyone help? I would like to find out how to find out what quenching time is needed to achieve bainite transformation (bainite hardening) in chromoly alloy steel 42CrMo4 (SAE 4140). For example when I use oil as quenching medium with constant 350°C and I then I dip chromoly workpiece with austenite temperature into it and I need to know for how long it should stay in the oil and if there is a max time that can not be exceeded.
so nice of you to post this
Very nice lecture sir. Well explained.
16:20 You said that "On faster cooling, the temperature range over which the transformation happens is lower than in slower cooling."; but instead the temperature range increases in faster cooling.
Like in the cooling lines you have drawn, the slower cooling line has a small temperature range(the vertical height) when compared to faster cooling.
I am confused here. Please help!!
What we mean is that at slower cooling the transformation starts at higher temperature.
Thank you very much. This video helps me a lot!
Sir since at temperature below and above the nose the transformation rate is small so shouldn't it be that the gap between start and finish curve along isotherm should be larger as compared to nose because larger the transformation rate less time it will take to transform
Sir what will we get on cooling at upper critical cooling rate (the cooling line just touch and pass to the Ts curve) ?
Sir why we get coarse grains on low cooling rate and fine grains on higher cooling rate?? What is the cause behind this sir ?
awsm explanation .....
Sir here at 16:19 the two cooling curve u took was it for water or alloy?because if its liquid water then its pure substance and pure substance solidifies at fixed temperature,if its alloy then how we are able to superimposed an alloy curve to an pure substance's TTT diagram?
This example is of a pure liquid. When we say a pure liquid freezes at a fixed temperature, we mean the temperature at which solid and liquid are in thermodynamic equilibrium. Freezing will happen at this temperature only if the cooling rate is extremely slow to allow for equilibrium to be attained. At normal or faster cooling rates undercooling is possible, i.e., the liquid will remain as a metastable liquid even below the equilibrium freezing temperature. This liquid can thus solidify at a temperature below the equilibrium freezing temperature.
@@rajeshprasadlectures thanx a lot sir 🙏
thank you sir for clear explaining.......
in heat treatment how liquid phase is coming?
In this videoTTT diagram is drawn for solidification and not for heat treatment.
thank you for that last interesting fact ;-)
Amazing teacher
Thank you sir. It's outstanding.
Sir, how the process of slow cooling or fast cooling is done practically?
Think of casting. Sand casting gives relatively slower cooling rate than die casting. And then there are techniques called rapid quenching where one cools so fast that one gets amorphous or glassy phase.
Indebted to u the GEM💎🙏🙏🙏
Maza hi aa gya sir .
Happy liquid 😂
the present teacher's of APL102(IITD) are very bad when compared to you sir ❤️
Super sir💥💥🤙
I love you!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Today I have MSE exam.... That's y i am here... 😄
Thanks sir.
Can you explain it little bit in hindi
gold
Kuch smjh me ni aaya
نعيما دكتور
I think this video lecture is the ultimate explanation of TTT diagram in my opinion! So detailed, elabroated, and thorough lecture. Thank you so much sir!
God bless you for this video, professors at Tier 3 universities can not match this even in their dreams.
Sir, your teaching content is unparallel. This is GOLDEN!
What happens if the cooling curve touches the start curve twice and never hits the finish curve?
Sir, will you please explain under what conditions it is called fast cooling and slow cooling? And if we do water quenched aluminum composite what will be the effects on grains, will it developed finer grains?
Lets see it for iron...Water quenching of austenite is fast. So it will give martensite directly(fast cooling). Oil quench will give very fine pearalite,air cooling will give fine pearalite. Nd furnace cooling will give coarse pearalite.
tommorow is our end-sem, thanks professor!
Thank you 🙏 so much sir... No need of going to college.. ,Your videos are more enough to gain knowledge..
Great video sir and you are also great ☺☺☺☺
Sir, thank you for your very nice explanation of TTT diagram, but i have a quesiton..
in this video, your diagram looks like CCT diagram, not TTT diagram because of the continuous cooling rate you draw...
so.. isn't it a CCT diagram??
You have asked a serious question. And that points to subtle point regarding the difference between TTT and CCT. The diagram I have drawn is a TTT diagram. The CCT diagram does not have the lower part of C curve. So strictly speaking I should not draw a continuous cooling curve on these diagrams. I avoided discussion on CCT diagrams in these videos. So I did not go into these details and loosely drew continuous cooling curve on a TTT diagram, which in a strict sense is incorrect.
@@introductiontomaterialsscience Ah.. now i see! Thank you so much for answering my question!
Below melting point how solid transfers to liquid
Wow What an explanation
best lecturee
Sir we've already seen that for an alloy, transformation occur at a range of temp.(except for eutectic composition)...but in TTT diagram phase transformation start and finished at the same temp...HOW IS THIS POSSIBLE??
Amazing explanation
Can anyone help me out
If two identical materials are cooled with same cooling rate but one is cooled from say 820 and the other from 790, transformation temp of former being higher ,will it have coarser grains?
Sir, I have a question. Why when you supercool the liquid, during the crystallization, does the temperature decrease? I think the temperature should be supposed to keep constant.
TQ so much sir
Best video for Materials Science even seen. Help me get through PhD qualifying exam
Sir is that glass is called as martensite?
And no doubt IIT is always good at teaching
Nive understandable Lecture Sir. Thank you sir👏👏
Ganda rei
Wow! thank you sir!!! May God bless you!!
Valuable lecture ....thank you sir
You make metallurgy very interesting, Sir! Thanks a lot.
Thanks for making this video
You are absolute Gem sir hats off to you
a very good explanation sir
this is fantastic.
Thanks so much sir
Sir, which property of glass distinguishes it from solid and make it more of a liquid
The distinction between crystal and glass is their atomic arrangement. In crystals the atoms are periodically arranged. Atomic arrangement in glass is disordered. The atomic arrangement of liquid is also disordered and in this sense, glass is compared to a liquid.
Nice lecture 👍
Was he saying about the transformation of water or any other substances
Awesome sir.. very student friendly teaching methodology... 🙌
Sir please provide notes
Overall course
7:15 Why would start of solidification late at lower temperatures?
You end up having so many grains that are so small they can’t really come together to form a solid
See previous video bro. At low temp, atomic mobility is less so the nucleation and growth rate is less.so more time required for nucleation and growth