Hi sir. 1.On what basis we can say that recrystallization will form finer recrystallised grains if degree of prior deformation is more. 2. In the definition it was mentioned as replacement of deformed crystal of high dislocation density. But we are speaking about nucleation in the further points, does that mean recrystallization as nucleation of dislocation free grains. 3. What is the actual mechanism of Recrystallization sir?
More the prior deformation more is the driving force for recrystallisation. Yes, recrystallisation happens with nucleation of stress-free grains in strained crystal.
Recrystallization process involves the nucleation of strain-free (or dislocation free) grains and their subsequent growth in the unrecrystallized matrix. This process involves the movement of the grain boundary between the recrystallized and the unrecrystallized grains.
Sir, you said Driving force: strain energy associated with dislocations. Does that mean Gibbs free energy associated with lower dislocation density will be greater than gibbs free energy associated with higher dislocation density?
During recrystallization no change of phase takes place. Strain free crystals form from the strained crystals of the same phase. so strictly speaking it is not an even a phase transformation. So it is microstructural transformation without any phase change. The mechanism of transformation is like nucleation and growth. Thus the rate of transformation depends on temperature. It is not martensitic where the rate is independent of transformation.
At higher temperatures, there are mechanisms by which dislocations and other defects can be annihilated. Thus strain energy associated with these defects is reduced.
Best possible explanation sir ...thanks
super explaination ..thank you...sir..
in recrystallization do annealing twins form and if they are formed ,in what structure
Hi sir.
1.On what basis we can say that recrystallization will form finer recrystallised grains if degree of prior deformation is more.
2. In the definition it was mentioned as replacement of deformed crystal of high dislocation density. But we are speaking about nucleation in the further points, does that mean recrystallization as nucleation of dislocation free grains.
3. What is the actual mechanism of Recrystallization sir?
More the prior deformation more is the driving force for recrystallisation. Yes, recrystallisation happens with nucleation of stress-free grains in strained crystal.
thnaks
Thanks a lot sir
Sir, I didn't understand the effect of solute atoms on recrystallization temperature - why do grain boundaries move during recrystallization?
Recrystallization process involves the nucleation of strain-free (or dislocation free) grains and their subsequent growth in the unrecrystallized matrix. This process involves the movement of the grain boundary between the recrystallized and the unrecrystallized grains.
tq
Sir,
you said Driving force: strain energy associated with dislocations.
Does that mean
Gibbs free energy associated with lower dislocation density will be greater than gibbs free energy associated with higher dislocation density?
No, it is the other way round.
Is recrystallization a martenistic or a nucleation growth driven phase transformation ?
During recrystallization no change of phase takes place. Strain free crystals form from the strained crystals of the same phase. so strictly speaking it is not an even a phase transformation. So it is microstructural transformation without any phase change. The mechanism of transformation is like nucleation and growth. Thus the rate of transformation depends on temperature. It is not martensitic where the rate is independent of transformation.
Sir why temp is exponential depends on recristalization.
What causes recrystallization? In energy
I also have the same question. Can recrystallisation occur on its own ?
energy stored in higher density dislocations, or strain energy associated with dislocation
Hi sir
I didn't understand the effect of recrystallization on tensile strength.
How does tensile strength decreases with recrystallization?
The decrease in strength is due to reduction of strain hardening due to decrease in dislocation density.
Because due to grain growth the course grain form and it is easy to deform . So tensile strength decrease
Sir how cold working at lower temperature will have higher strain energy than at more temperatures.. Pls explain...
At higher temperatures, there are mechanisms by which dislocations and other defects can be annihilated. Thus strain energy associated with these defects is reduced.
@@rajeshprasadlectures thank you sir for the explanation